Mr Gibson's daughter Tina Gibson, herself an architect now working in Luxemborg, has also voiced her opposition to the high-rise plans and has started a Facebook page titled Queensland Cultural Centre Campaign protesting the state government's alterations to her father's designs. "Essentially it is a myriad of inappropriate commercially driven alterations and additions that will inalterably affect both the interior and the exterior of the Complex," Ms Gibson told Fairfax Media. "To make matters worse the funding for all these changes will come from selling off the airspace above and constructing a pair of 30-storey towers," she said. "The scheme is a travesty and should be stopped." The Institute of Architects has called for a Conservation Management Plan to be put in place, so decisions about the proposed changes to the site can be evaluated against Mr Gibson's original architectural vision.

The Queensland government allowed seven weeks for public consultation on the draft plan. The cultural precinct was first called Queensland's Cultural Centre and includes the Queensland Performing Arts Complex, the Queensland Art Gallery, Queensland Museum and State Library. Mr Gibson died in March 2014, aged 84, a month before the plan was released. In August, the Australian Institute of Architects lodged an application to have the site – minus the State Library because it has recently been modernised – added to Queensland's Heritage Register. In that application, the institute highlights that one of the guiding principles of Mr Gibson's design brief was "low-profile architecture, respecting the encompassing hills of greater Brisbane".

Richard Kirk, president of the Queensland branch of the Australian Institute of Architects, said the government's master plan for the site had no Conservation Management Plan. "Chiefly our concern was that the Master Plan, even though it was a 20-year master plan, proposed numerous changes to the buildings based on a current brief, not on a longer-term brief," he said. The institute has also objected to the plans for the two high rise buildings. "The thing that we don't believe would be supported at any level, will be the addition of those high-rise buildings in the precinct," Mr Kirk said. He said the institute believed the low-rise nature of Mr Gibson's public realm for the premier culture precinct should remain low-rise.

"You typically don't build over large span structures like a performance space or a museum, particularly with a tower. "They are undesirable from a conservation point of view, they are undesirable from an urban point of view and they are clearly unworkable from a financial point of view." "We think they are unfortunately inappropriate on any level." Arts Minister Ian Walker on Monday said it backed the institute's request to have the cultural precinct included on Queensland's heritage register. But he declined to comment on the proposed towers.

"The government would support a heritage listing that acknowledged the importance of this place to the cultural life of Queensland and the need to preserve its active role in the future," Mr Walker said. That would include a Conservation Management Plan for the Queensland Cultural Centre site. "A Conservation Management Plan is required for the management of heritage-listed sites," Mr Walker said. "Arts Queensland will be preparing a Conservation Management Plan during the coming months which will be submitted to the Queensland Heritage Council for consideration as part of the heritage assessment process." However, the state government will not wait until the Conservation Management Plan is finalised, before pushing ahead with development at the cultural precinct, Mr Walker said.

He cited Brisbane's RNA site as an example of a site where architectural and heritage aspects were being considered, while development of the site continued. The Ekka site at Bowen Hill was listed on the Queensland Heritage Register in July 2003. Yet, Mr Kirk said the analogy was inappropriate, because the RNA site and the cultural precinct were completely different. "It completely misses the point, to compare the rarity of these buildings," Mr Kirk said. "We maintain that these buildings are among the top 10 most important buildings in the national estate and they needed to be treated accordingly."

"They need to be treated with a long-term vision." Submissions on the application to have the Queensland Cultural Precinct heritage-listed close Friday, September 19.