Boris Johnson: Price of quitting EU is 'lower than ever'

The price of quitting the European Union is "lower than it's ever been", Boris Johnson has claimed.

Speaking in Japan, the London Mayor and Conservative MP refused to rule out spearheading the 'Out' campaign.

But he argued it was better for the UK to stay in a reformed EU, saying he backed David Cameron in his efforts to secure change ahead of the referendum.

Mr Johnson's comments come on the day the In campaign, Britain Stronger in Europe, launched its campaign.

He also indicated the prime minister would be setting out more details about Britain's attempts to renegotiate its terms of membership of the EU "in the next few weeks".

A date has not been set for the referendum, but Mr Cameron has promised to hold the in-out vote by the end of 2017 at the latest.

During a visit to Osaka in Japan, Mr Johnson was asked where he stood on Britain's in-out referendum on EU membership.

"I think I am exactly where the prime minister is and, I think, actually a huge number of the proportion of the British public.

"We want, in an ideal world, to stay in a reformed European Union but I think the price of getting out is lower than it's ever been. It's better for us to stay in, but to stay in a reformed EU. That's where I am," he said.

The MP, who is touted as a potential future Conservative leader, said he had "great faith" in Mr Cameron's negotiations to secure EU reform, describing him as "a fantastic bridge player [and] negotiator".

"In our party we're backing the prime minister. I think he's got every chance of getting a good deal," he said.

But Mr Johnson also cautioned that it was sensible not to rule out walking away from the table in the negotiations.

"You have to wait and see what the deal is going to be. But I've got great faith in the prime minister," he said.

On Sunday, UKIP leader Nigel Farage said it was possible that Mr Johnson could head the Leave.EU campaign, but the London mayor told the BBC he was unaware of the Eurosceptic's overtures.

"News of this pronouncement has not detonated over [Japan] like a thunderclap. I don't know about these invitations," he said.