Non bio-degradable plastic is blamed for environmental problems
A UN-backed study found that two million plastic bags were handed out each year in Nairobi alone - where only a quarter of daily waste is collected.
Many bags are so thin they last only one shop, and have to be discarded.
Backing action, Kenya's Nobel laureate Wangari Maathai said drains and sewers were being blocked - creating breeding areas for malaria-carrying mosquitoes.
Discarded bags also choke farm animals and marine wildlife and pollute the soil, the study into Kenya's solid waste management found.
The bags can take between 20 and 1,000 years to decompose.
The report comes as governors of the UN Environment Programme (Unep) hold their 23rd conference in Nairobi.
Kenya's Institute for Public Policy Research and Analysis and the National Environment Management Authority were also involved in the study.
Tree-planting
More than 48 million thin plastic bags are produced in Kenya each year, and production is increasing to meet consumer demand, the study found.
"Flimsy plastic shopping bags should be banned and a hefty levy slapped on thicker ones to rid Kenya of an increasing environmental and health menace," Unep said.
Earlier this week, Kenyan President Mwai Kibaki reportedly told Unep officials that his government would tackle the problem.
Professor Maathai sought support for her tree-planting campaign
"If I had my way, we would have started that immediately," she said.
Also at the conference, Ms Maathai, who won the Nobel Peace Prize last year, called on developing nations to support the Kyoto Protocol on climate change.
Ms Maathai, who is credited with planting more than 30 million trees around Africa, has urged other nations to join her tree-planting campaign.
"What we should do to ensure that the Kyoto Protocol is successful is to plant a lot of trees in order to create carbon sinks," she said.
They are cheap, useful, and very plentiful, and that is exactly the problem, according to researchers. A report issued on Feb. 23 by a cadre of environment and economics researchers suggested that Kenya should ban the common plastic bag that one gets at the checkout counter of grocery stores, and place a levy on other plastic bags, all to combat the country's environmental problems stemming from the bags' popularity.