Prominent campaigners, politicians and scientists have called for Canada to be suspended from the Commonwealth over its climate change policies.

The coalition's demand came before this weekend's Commonwealth heads of government summit in Trinidad and Tobago, at which global warming will top the agenda, and next month's UN climate conference in Copenhagen. Despite criticism of Canada's environmental policies, the prime minister, Stephen Harper, is to attend the Copenhagen summit. His spokesman said today: "We will be attending the Copenhagen meeting … a critical mass of world leaders will be attending."

Canada's per capita greenhouse gas emissions are among the world's highest and it will not meet the cut required under the Kyoto protocol: by 2007 its emissions were 34% above its reduction target. It is exploiting its vast tar sands reserves to produce oil, a process said to cause at least three times the emissions of conventional oil extraction.

The coalition claims Canada is contributing to droughts, floods and sea level rises in Commonwealth countries such as Bangladesh, the Maldives and Mozambique. Clare Short, the former international development secretary, said: "Countries that fail to help [tackle global warming] should be suspended from membership, as are those that breach human rights."

The World Development Movement, the Polaris Institute in Canada and Greenpeace are among the organisations supporting the plan. Saleemul Huq, a lead author for the Intergovernmental Panel on Climate Change, said: "If the Commonwealth is serious about holding its members to account, then threatening the lives of millions of people in developing countries should lead to the suspension of Canada's membership immediately."

Canada's environment department refused to comment on the call for it to be suspended.

The Commonwealth comprises 53 states representing 2 billion people. In the past it has suspended Pakistan, Zimbabwe, Nigeria and South Africa for electoral or human rights reasons. Speaking earlier this week, its secretary general, Kamalesh Sharma, said: "I would like to think that our definition of serious violations could embrace much more than it does now."