Radiohead are to play a benefit concert for Friends of the Earth

Yorke is an ambassador for Friends of the Earth, who asked him to put his views to Mr Blair in September.

The singer told the NME he declined because he thought the prime minister had "no environmental credentials".

He also said he got "freaked out" by preliminary discussions with Mr Blair's advisers.

As well as backing the Friends of the Earth Big Ask campaign, calling for a cut in greenhouse gas emissions, Yorke has protested against global trade laws and the Iraq war.

It was like talking to Blair's spin doctors - it was all getting weird Thom Yorke

Explaining why the meeting did not take place, the star told the magazine: "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, ie 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."

'Shallow' touts

Radiohead will play a benefit concert for the Friends of the Earth campaign at London's Koko club on 1 May.

Yorke has also attacked "shallow" people selling tickets for the show for up to £150 on eBay.

"Might I suggest that those selling their Koko tickets on eBay for stupid money gives a contribution..." he wrote on the band's website.

"Say 30% of their proceeds, back to Friends of the Earth, for whose benefit we are all doing this show. Seems only fair."