TORONTO - Four of the country's former prime ministers have co-signed a statement demanding more be done to tackle climate change in Canada.

Paul Martin, Joe Clark, Kim Campbell and John Turner issued a joint statement today with a lost of business, academic and other leaders.

Clark says he is "very concerned" by a lack of decisive action on climate change and that Canada is "falling further behind."

He adds Canada "cannot afford another round of posturing and denial" and a clear and honest commitment is needed for strong, simple and effective climate laws."

Campbell says when it comes to tackling climate change, "there has been a persistent void at the highest political levels in this country."

Two prime ministers did not sign the document from a group called Canadians for Climate Leadership entitled "Time To Get Serious on Climate Change" -- Jean Chretien and Brian Mulroney.