A Labour MP has accused fellow MPs of being "out to lunch" on climate change as he announced he would quit Parliament at the next election.
Alan Simpson - a leading critic of Tony Blair from the left of the party - said he wanted to join more effective campaigns outside Westminster politics.
He wrote to members of his Nottingham South constituency informing them he would not stand again after nearly 15 years as an MP.
One of the founders of the Labour Against The War meeting, he has been a consistent and vocal opponent of the Iraq war which he dubs a "criminal offence".
A serial rebel in Commons votes, he was disciplined for saying replacing Tony Blair with Gordon Brown as Labour leader would be like replacing Saddam Hussein with one of his sons.
But he said that global warming - and Parliament's failure to tackle it properly - was his main concern in deciding to quit.
He said: "We have probably got 10 maybe 15 years maximum to make some huge fundamental changes in the way we organise society if we are going to manage our way through the worst aspects of climate change. And I think Parliament is out to lunch on this.
"There are so many of the really big challenges that Parliament has just lost the courage to address. Instead, the thinking is being done outside, by cities, by regions, by international alliances, between different community movements.
"If the momentum of Parliament is as detached as it has been so far about climate change and the failure to make these changes now, then I do not want to be a part of that cover-up."
He has been particularly infuriated by Mr Blair's determination to press ahead with a new generation of nuclear power stations and to keep the UK's nuclear deterrent.
