Joe Clark, shown in August 2001, and three other former prime ministers are among those who have signed a document demanding urgent action on climate change. ((Tom Hanson/Canadian Press))

Two days into the campaign for the Oct. 14 federal election, four former prime ministers have joined a coalition of Canadians demanding urgent action on climate change.

The group of about 60 business people, academics and environmentalists calling themselves Canadians for Climate Leadership is set to release a document Tuesday entitled Time To Get Serious on Climate Change.

The report calls for a $30-a-tonne price tag on emissions, and says a "staggering" investment in green technologies is required.

The document has been signed by four former prime ministers, Joe Clark and Kim Campbell, both Progressive Conservatives, and Liberals Paul Martin and John Turner.

"We simply can't afford another round of posturing and denial in this next election," said Clark in a news release Monday.

"Climate change shouldn't be dealt with as a political football," Nova Scotia businessman John Roy, who helped draft the report, told CBC news.

The report stops short of endorsing the Liberals' Green Shift carbon plan, which would offset a tax on emissions with income tax cuts, but Roy said funds generated by an emissions tax must be redistributed to those who would be hit the hardest.

The names of Jean Chr├ętien and Brian Mulroney are conspicuously absent from the document, even though both were contacted by the group, Roy told the Globe and Mail.

Chr├ętien was not immediately available for comment and a Mulroney spokesman said staff in his Montreal office indicated they had no recollection of receiving such a request.

With files from the Canadian Press