Al Gore has made his sharpest attack yet on the George Bush presidency, describing the current US administration as "a renegade band of rightwing extremists".

In an interview with the Guardian today, the former vice-president calls himself a "recovering politician", but launches into the political fray more explicitly than he has previously done during his high-profile campaigning on the threat of global warming.

Denying that his politics have shifted to the left since he lost the court battle for the 2000 election, Mr Gore says: "If you have a renegade band of rightwing extremists who get hold of power, the whole thing goes to the right."

Mr Gore, who appeared at the Guardian Hay literary festival over the bank holiday weekend, is promoting An Inconvenient Truth, a documentary and book detailing the climate change crisis that he warns "could literally end civilisation".

In the interview Mr Gore also distances himself from Tony Blair on the subject of nuclear power, which the prime minister has insisted is "back on the agenda with a vengeance". Mr Gore says he is "sceptical about it playing a much larger role," and that although it might have a part to play in Britain or China, it will not be "a silver bullet" in the fight against global warming.

Before President Bush touched down in Pennsylvania Wednesday to promote his nuclear energy policy, the environmental group Greenpeace was mobilizing.

"This volatile and dangerous source of energy" is no answer to the country's energy needs, shouted a Greenpeace fact sheet decrying the "threat" posed by the Limerick reactors Bush visited.

But a factoid or two later, the Greenpeace authors were stumped while searching for the ideal menacing metaphor.

We present it here exactly as it was written, capital letters and all: "In the twenty years since the Chernobyl tragedy, the world's worst nuclear accident, there have been nearly [FILL IN ALARMIST AND ARMAGEDDONIST FACTOID HERE]."

Had Greenpeace been hacked by a nuke-loving Bush fan? Or was this proof of Greenpeace fear-mongering?

The aghast Greenpeace spokesman who issued the memo, Steve Smith, said a colleague was making a joke by inserting the language in a draft that was then mistakenly released.

"Given the seriousness of the issue at hand, I don't even think it's funny," Smith said.

The final version did not mention Armageddon. It just warned of plane crashes and reactor meltdowns.