We write as a matter of urgency regarding the arbitrary detention of the Chinese artist Ai Weiwei (Report, 7 April). We and many Chinese and other friends are very concerned at the Chinese government's behaviour towards its own citizens. Ai Weiwei's position is that he firmly believes in the freedom of speech and the right to speak up on behalf of others who have been brutally silenced for their efforts to change society for the better.

As an immediate priority we urge governments to exert strong pressure on China to treat its citizens with respect as a matter of basic justice and humanity. At this stage of China's development as a country taking an increasing part in world affairs, it is crucial that we make it clear that China's credibility in the world is at stake if it does not significantly improve its human rights record.

For example, another artist, Wu Yuren, was released in Beijing on 3 April after being detained for nearly 11 months without trial. His wife and child were left in a state of great anxiety for his safety and welfare and he had committed no crime. Liu Xiaobo has been handed an 11-year sentence as a writer who expressed the need for constitutional reform in the Chinese political system. He has effectively been removed from society for more than 10 years for expressing his views.

We are concerned that the same fate awaits Ai Weiwei. We urge the UK government to treat this case as an urgent priority and to press for his immediate release.

Katie Hill (Curator and Lecturer, Chinese Contemporary Art)

Cai Yuan (Artist)

Ma Jian (Author, Beijing Coma)

Jung Chang (author, Wild Swans)

Jon Halliday (Historian)

Craig Clunas (Professor of Art History, University of Oxford)

Michael Stanley (Director, Modern Art Oxford)

Jayne Parker (Head of Graduate Fine Art Media, Slade School of Fine Art)

Adrian Searle (Critic)

Gao Brothers (Artists, Beijing)

Iwona Blazwick (Director, Whitechapel Gallery)

Tehching Hsieh (Artist)

Greg Hilty (Lisson Gallery)

John Gittings (Writer)

Rob and Roberta Smith (artist)

Kathy Battista (Programme Director, Contemporary Art, Sotheby's Institute)

JJ Xi (Artist)

Britta Erickson (Chinese art specialist and curator)

Alison Craighead (Artist)

Fabio Rossi (Director, Rossi & Rossi Gallery)

Langlands & Bell (Artists)

Siu Lan Ko (Artist)

Prateek Raja

Chris Berry (Professor of Film Studies, Goldsmiths)

Voon Pow Bartlett

Esther Menon

Eunice Yu (MYU projects)

Sarah Macdonald

Cameron Eeles

James Robertson (Writer)

Jo Ahern

Siobhan Doran

Sharon McCulloch

Fawz Farhan

Anna Allalouf

Richard Allalouf

Ciaran Daly

Jennifer McGuire

Jenny McConnel

Julie Rogers

Malu Halasa

Stella Hurtado

Jean Madgwick

Susan Whitehead

Leah Garnett

Roman Ondak (Artist)

Lisa Hanover

Isaac Julien (Artist)

Penny Spurbund

Julia Carver

Jill Hartz

Haili Sun (Artist)

Xiaoping Sun

Kate Edwards

Manuela de Laborde

Kathryn Lloyd

Tess Fitzjohn

Susan Collins

Richard Noble (Professor, Goldsmiths College)

Sarah Keeling

Maitreyi Maheshwari

Miriam Wiesel

David Ka-Shing Tse (Director, Chinatown arts)

Lisa Goldman

Gerard Choy (Artist)

Grace Gelder (Photographer)

Kevin McLoughlin (Curator of Asia, National Museum of Scotland)

Wenny Teo (Scholar)

Julie Segraves (Curator)

Andy Field

Paddy Johnson

Griselda Pollock (Professor of Art History, Leeds)

Sharon Sinclair

Stephanie Houde

Keith Wallace (Editor, Yishu Journal of Contemporary Chinese Art)

Polly Kwong (Artist)

Isabella Maidhead

Timothy Birch (Writer)

Keith Whittle (Director, Fountain Art)

Wessie Ling (Artist)

Sangita Mulji

Ann Twiselton (MIT Press, London)

Julia Carver

Augusto Corrieri

Owen Parry

Stefan Szczelkun

Catherine James

Samir Pandya

John E Owens (Professor of Politics, University of Westminster)

Rosie Thomas (Director, CREAM, University of Westminster)

Nat Hunter (Designer, Airside)

Blaise Drummond (Artist)

Jeroen de Kloet (China scholar and curator)

Diana Yeh (Writer)

Anna Soranzo

Sarah Cheang (Art historian, London College of Fashion)

Lois Keidan (Director, Live Arts Development Agency)

George Dawei Guo

Benedict Ramos (Photographer)

Nathan Thomas

Teresa Cisneros

Emily Pethick

Holly Willats

Doreen Mende

Jeremy Chu

Emily Smith

Melanie Manchot

Neil Sansom

Helena Wee

Annie Lok

Moti Roti (Artists)

Clemmie Marshall

Benben Hill-cai

Louis Hill-cai

Louisa Pearson

Lisa Hanover

Thomas Eller

Rachel Lucy King

David Thorp (Curator)

Rob Hadrill

Tarikh-Oliver Bull

Sheyma Ettefagh

Carole Sabas

Richard Croxford

Paul Chauncy

Mark Ball

Lisa Le Feuvre

Laura McLean-Ferris

Anne Katrine Dolven

Annie Lloyd

Nina Miall

Alison Harvey

Jason Bowman

Sue Jones

Abigail Sidebotham

Dave Farnham

Simone Kenyon

Manick Govinda (Curator, Artsadmin)

Hwang Eunhye

Matt Calderwood

Gregory Mosher

Isabel Paterson

Hannah Knights

Matt Watkins

Birgit Spies

Lucy Badrocke

Rebecca Partridge

Laura Godfrey Isaacs (Curator)

Jonathan Ashworth

Tim Knowles

Anna Lo

Molly Taylor

Eva Ting (Curator, TwoCities Gallery, Shanghai)

Anthony Elliott (Curator)

Hilary Crisp

Elisabeth Nelson

Christian Marclay

Lucy Mercer

Ian Brown

Caitlin Tebbit

Harvey Cohen

Paul Luckratt

Eliza Gluckman (Curator)

Lucy Day (Curator)

Deh-I Hsiung

Victoria Munro

Claudia Albertini (Curator)

Abel Ségrétin

Martin Kemp (Emeritus Professor of the History of Art, University of Oxford)

Carolyn Black

Holly Black

Stephanie Kirkness

J Whalen Bridge

Alison Clarke

Kelly Wojtko

Viola Götz

Nicky Wheeler

Manja Krech

Nigel Llewellyn

Matt Price

Yuehping Yen

Jas Elsner

Maya Schweizer

Clare Hills-Nova

Katrin Macmillan

Izumi Yuu

Camilla Pearson

Matthias Kispert

Gerard Faggionato

Louis Eastwood

Jay Ridings

Umi Baden-Powell

Melissa Lam

Rhianon Morgan-Hatch

Elizabeth Bromley

Bradley Phillip

Kasia Fijalkowska

Philip Watson

Anna Merton Kan

Verity Wilson

Rachel Marshall

Dr. Clare Harris (Art historian)

Eyawn Harry

Raksha Patell

Pamela Skelton

Mariele Neudecker (Director, Neudecker Gallery)

Peter Davies

Mike Tsang

Annette Lord

Sally Joyston-Bechal

Ellen Mara De Wachter

Michael Walling

Emma Talbot

Dave Cross

Stuart Jones

José A. Sánchez

Tim Etchells

Rose Issa (Curator)

Caragh Quinlan

CJ Mitchell

Cecilia Wee

Gini Simpson

Sue Giles

Erika Tan (Artist)

Debra Wacks

Franziska Koch

Christine Robertson

Grace Lau (Artist)

Dinu Li (Artist)

Anne Odling-Smee (Designer)

Mary Ryan

David Elliott (Curator)

Gervase Rosser

Mary Hill

Alice Mills

Christopher Horrocks

John B. Turner (photographer)

Sarah Hymas

Eric Fong (artist)

Cao Fei (artist)

Victoria Brown

Julian Ward

Anthony Roberts (Director, Colchester Arts Centre)

Amelia Beatty

Ben Lewis

Fiammetta Rocco

Hanneke Grootenboer

Adam Chodzko (artist)

Antonia Mexcua

Malcolm Bull

Pasco Q Kevlin

Jonathan Murray

David Campany (photographer)

Miriam Manook

Jeffrey Wasserstrom (China scholar)

Sylvio Nery

Rob La Frenais (Curator, The Art Catalyst)

Frank Dikötter (author, China's Great Famine)

Jon Kear

Nikki Tomlinson

Paul Carey-Kent

Alicia Paz

Fleur Donnelly-Jackson

Claire Doherty

Grace Sherrington

Thomas Clark

Layla Curtis

Julie Umerle

Claire MacCrory

Emma Kelly

Katie Paterson

Roisin Byrne

Karen Wright

Marco Filippini

Jeremy Deller (artist)

Anne Gerritsen

Mei Yuk Wong

Joanne Greenbaum (Artist)

Taylor Trabulus (Artist)

Caryn Coleman (Curator)

Lauren Weinberg (Art & Design Editor, Time Out Chicago)

Jamie Sterns (Director, PPOW Gallery)

Ron Hogan (Writer and Blogger)

Rachel Selekman (Artist)

Alyce Santoro (Artist)

Lisa Cooley (Director, Lisa Cooley Gallery)

Rachel Mersky (Artist)

Caren Golden (Director, Caren Golden Fine Art)

Louky Keijsers Koning (Director, LMAKprojects)

Aileen Tat (Artist)

Greta Kuriger (Archivist)

Jennifer Sanchez (Artist)

Jeffrey Baij (Artist)

Michael Gillespie (Director, Foxy Production)

Priya Bhatnagar

Julia Halperin (Writer, New York Observer)

Nora Gomez (The Alliance for Young Artists and Writers)

Tracey Harnish (Artist)

Paul Schmelzer (Managing Editor, American Independent News Network)

David Carson (Typographer)

Alexis Tryon (CEO, Artsicle)

Eva Kenny

Sally McKay (Artist)

Matt Held (Artist)

Judith Braun (Artist)

Jacqueline Mabey (Writer)

Rachel Stevens

Sheila White (Artist)

William Schefferine (Artist)

Charles Gute (Artist)

Helen Dennis (Artist)

Kathryn Smith (Artist and Curator)

Kelli Miller (Designer)

Man Bartlett (Artist)

Jennifer Dalton (Artist)

Torben Zenth (Kopenhagen.dk)

Perry Bard (Artist)

Sally Williams (Brooklyn Museum)

Matthew Gaffney (Artist)

Andrew Russeth (Critic, 16 Miles of String)

James Joyce (Artist)

Renee Vara (Vara Fine Arts)

Nathalie Herling

Joyce Pommer (Artist)

Dan Levenson (Artist)

James Wintner (CEO, BenefitEvents)

Michelle Forsyth (Associate Professor, Washington State University)

Michelle Vaughan (Artist)

Ian Ferrier

Madeline Warren

Natalie Moore (Artist)

Kate Wilson (Artist)

Grace Johnstone (Artstar)

Benjamin Tischer (Director, Invisible-Exports)

Elaine Kaufmann (Artist)

Erik Parker (Artist)

Randy Wray

Daniel Wilson

Alexis Hubshman (President, Scope Art Fair)

Jane Deschner (Artist)

Tyler Carter (Writer)

Monica Lundy

Rebecca Taylor (Arts Blogger, The Huffington Post)

Judith Page (Artist)

Peter J. Russo (Editorial and Program Director, Triple Canopy)

Heather Bhandari (Director, Mixed Greens Gallery)

Amy Talluto (Artist)

Mark Holdrege

Susan Smith Rosenthal

Fiona Gardner (Artist)

Leah Sandals (Writer)

Chloe Pantazi

Nicole Eisenman (Artist)

Amy Bennett (Artist)

Michael (Art Observed)

Courtney Strimple (Exhibitions Coordinator, Mixed Greens Gallery)

Poppy Gordon Lennox

Lisa Moon

Siobhan Burke

Julie Peppito

Forrest Nash (Editor, Contemporary Art Daily)

Elizabeth Zans

Svea Lin Soll (Director, Swarm Gallery)

Caroline Dumalin

Nickolus Meisel (Assistant Professor, Washington State University)

Kevin Zucker (Artist)

Rebecca Loyche (Co-Director, Co-Verlag)

John Zeppetelli (Curator, DHC/ART)

Cheryl Sim

Emily Vey Duke (Assistant Professor, Syracuse University)

Olen Hsu (Artist)

Annie Rana (Director, Marianne Boesky Gallery)

Lyle Rexer (Curator and Writer)

Doug Garth Williams (Artist)

Alice Gray Stites (Curator)

Laura Sandoval

Shelley Marlow (Photographer)

Thomas Jaeckel (Director, 532 Gallery Thomas Jaeckel)

Brainard Carey (Director, The Artworld Demystified)

Sholeh Asgary

Borbay (Artist)

Edith Bolton

AMI Miami (Design)

Sophie Leininger (Artist)

Alana Amram (Musician)

Whitney Jordan (Artist)

Emily Falvey (Curator)

Diana Nemiroff (Director, Carleton University Art Gallery)

Cathy Busby (Artist)

Garry Neill Kennedy (Artist)

Cindy Baker (Programme Coordinator, AKA Gallery)

Dennis Cordell (Photographer)

Howard Johnson

Steve Loft (Trudeau National Visiting Fellow, Ryerson University)

Jennifer Gheith (Critic)

Carly Murphy

Deborah Kass (Artist)

Martha Moszczynski

Tina Newlove (Artist)

Jeanette Doyle (Artist)

Danielle Mysliwiec (Artist)

Ariel Goldberg (Artist and Writer)

Bobby Lukas (Artist)

Chris Fraser (Artist)

Chloe Wyma

Jana DesForges (Director, BLK/MRKT Gallery)

Scott Fulmer

Suzan Frecon (Artist)

Lisa Sigal (Artist)

Myriam Vanesch (Artist and Writer)

Peter Herley (Artist)

Barbara Petro Escobar (Curator)

Ellie Buttrose (Writer)

Sirui Yan (Salon 94)

Santina Amato (Artist)

Krista Knapp (Designer)

Filip Noterdaeme (Director, Homeless Museum of Art)

Kasey Lindley (Artist)

Amanda Slack-Smith (Artist)

Vicky Colombet (Artist)

Roger White (Artist)

Caroline Elizabeth Babson (Curator)

Rebecca Layton (Artist)

Michael Walsh (Artist)

Chase Granoff (Artist, Choreographer and Curator)

Kate Stirr (Artist)

Ava Roy (Director, We Players)

Ellie Irons (Artist)

Deborah Margo (Artist)

Shihoko Iida (Curator)

Kathryn Weir (Curator and Head of International Art, Queensland Art Gallery)

Tirtzah Bassel (Artist)

Diana Kingsley (Artist)

Karen Hatch (Photographer)

Lori Waxman (Critic)

Leah Stuhltrager (Director, Dam, Stuhltrager Gallery)

Doug E. Roberts (Director, Mixografia Workshop)

Charles Beronio (Artist)

Lauren Silberman (Artist)

Donna Billick (Artist)

Kathryn Faulkner

Isabel Dreyer

Susan Chan Egan

Boris Austin (Photographer)

Holli Cooper

Manuela de Laborde

Mary-Jane Ng

Orlagh Woods (Co-Director, New Work Network)

Ai Xiaoming (Professor and filmmaker, Sun Yatsen University, Guangzhou)

Adriane Battaglia

Tanya Barrett

Hazel Muir

John Condon

Rustyna Edwards

Kate Newnham

Leslie Johnson (Director, Valand School of Fine Arts, Göteborg, Sweden)

Flore Nove-Josserand

Haegue Yang

Michael Duffy

Dr. Alice Correia (Gimpel Fils)

Michael Duffy

Judith Knight (Director, Artsadmin)

Estelle Holland

Erica Ornato

Gianni Barucco

Susan Hill

Robin Hill

Jane Bowen (Artist)

Dylan Bowen (Artist)

Arthur Bowen

Sarah Pickering (Teaching Fellow in Photography, Slade School of Fine Art)

Deirdre O'Mahony (Programme in Art and Design, GMIT, Galway, Ireland)

Joon Lynn Goh (Battersea Arts Centre)

Stephen Williamson

Richard Williamson

Dr. Patricia Lyons

Tania Mouraud (Paris)

Nicolas Aiello

Eric Alliez (Professor of Philosophy, Paris)

Joshua Loftin

Bernadette O'Donnell

Xenia Piëch (Writer and curator)

Peter Fraser (Insight Education)

Dragoljub Nesic

Loraine Baud

Simon Steven

Kai Syng Tan

Kwanyi Pan

Jean Cameron (Director, Visual Arts Festival, Glasgow)

Ynaiê Dawson

Beatrice Bonafini

Julia Whitehead

James Bluemel

Jaymz Wong

David Smith

Astrid Mahrer

Jeremy Mahrer

John Tucker

Beth Keeble

Rekha Pandy

Manu Pandy

Paul Edwards

Christine Edwards

Flora Drew (Translator)

Catherine Allen

Mary Knowles

John Cayley

Harriet Evans (Professor of Chinese Studies, University of Westminster)

Jeremy Lee (Artist)