London Mayor demands pared back EU links for Britain

By Kate Holton and Guy Faulconbridge

LONDON (Reuters) - London Mayor Boris Johnson heaped pressure on Prime Minister David Cameron on Tuesday by calling for a referendum on a deeply pared back British membership of the European Union.

Johnson, speaking at a Thomson Reuters Newsmaker event, said the euro was a calamitous project and that Britain should negotiate a new treaty to prevent its slide out of the world's biggest economic area.

"Boil it to down to the single market, that's the great achievement of the European Union, I think we could easily scrap the social chapter, the fisheries policy," Johnson, a Conservative party member seen as a potential rival to Cameron, said in a speech.

"That is a renegotiated Treaty we could and should put to the vote of the British people.

"It is high time that we had a referendum, and it would be a very simple question. Do you want to stay in the EU single market - yes or no?"

Johnson sidestepped three questions on whether he would like to be a future prime minister but he has set a high bar for Cameron. Negotiating such a new deal with Europe would be extremely difficult with EU allies unlikely to approve such a radical treaty change.

"There will be a huge barrage from foreign legations saying 'this is not on the table, there is no way we'll accept this'," said Johnson, a formidable campaigner whose messy mop of platinum blond hair makes him instantly recognizable.

"The choice is going to be very simple: it's between staying in on our terms or getting out," he told an audience of investors and bankers.