The singer is an ambassador for Friends of the Earth and the charity asked Yorke to meet the Prime Minister to talk about environmental issues.

But Yorke dismissed Blair as a man with "no environmental credentials" and said dealing with Labour "spin doctors" had made him feel ill.

Explaining why their meeting did not come off, the star told the NME: "Luckily, in the end the decision was kind of made for me.

"There's this whole thing going on at the moment with Blair and the nuclear thing. This all started kicking off about two or three weeks before I was supposed to meet with Blair, which I was not happy about anyway for obvious reasons, i.e. Iraq.

"It was, 'If we could just have a meeting beforehand where we could go through how it would proceed...'. It was like talking to Blair's spin doctors. It was all getting weird. It was just obvious there was no point in meeting him anyway, and I didn't want to.

"That was the illest I'd ever got. I got so stressed out and so freaked out about it. Initially when it came up I tried to be pragmatic. But Blair has no environmental credentials as far as I'm concerned.

"I came out of that whole period just thinking, I don't want to get involved directly, it's poison. I'll just shout my mouth off from the sidelines.

"It's a nasty business. It's up to people with pure integrity who know what they're talking about, like Friends of the Earth."

Yorke is backing the charity's Big Ask Campaign, which is calling for a cut in greenhouse gas emissions.

Radiohead will play a benefit gig for the campaign at London's Koko Club on May 1.