UK withdrawal from the European Union would not be as "cataclysmic" for British jobs as supporters of membership claim, London Mayor Boris Johnson has said.
Mr Johnson was speaking amid growing pressure on David Cameron over Europe, with Tory grandees like Lord Lawson and Michael Portillo advocating withdrawal and backbenchers hoping to force a Commons vote next week in protest at the Prime Minister's failure to table legislation to pave the way for a referendum.
The Mayor said he did not back Lord Lawson's call for the UK to quit the EU, but said that Britain must be ready to leave if Mr Cameron's plan to renegotiate its membership following the 2015 general election does not bear fruit.
Mr Johnson told BBC Radio 4's Today programme: "My position is that I think the Prime Minister is completely right. What we need to do is to say to our friends and partners `Listen chums, this thing isn't working for either of us. Your eurozone is causing all sorts of misery, plus the on-costs, the non-wage costs, of the way the EU has been running and has legislated and regulated over the last 20-30 years are making the whole area completely uncompetitive. We need a renegotiation. We need a look at the way the thing is managed'.
"We should be prepared to pull out. That goes without saying. You can't go into a negotiation like that without being willing to walk away."
Mr Johnson insisted that withdrawal would not be as damaging to the UK economy as pro-Europeans claim.
"I don't think it would be anything like as cataclysmic as is being sometimes pretended," he said.
"I don't think we would lose millions of jobs. I think the economic benefits and disbenefits are now much more balanced."