BORIS Johnson, the leading Vote Leave campaigner, has said he is "profoundly unhappy" with Nigel Farage's controversial immigration poster and he does not want the votes of the far right.

His remarks came as George Soros, the billionaire market trader, warned a vote to Leave the EU would trigger a plunge in the pound greater than Black Wednesday and Li Ka-shing, one of Asia's richest men, came out in favour of Britain remaining in the European Union, warning that a vote to leave would be "detrimental to the UK".

In a sign of the deepening rift between different parts of the pro-Brexit camp, Mr Johnson repeatedly refused to discuss the Ukip leader, who is part of the rival Leave.EU group.

Asked about rumours that Mr Farage might have a place in a Johnson government, the former London mayor appeared to renounce any ambition to be prime minister, telling LBC radio: "There's never going to be such a thing. This is not about me. This is about a fundamental decision that the British people have to make."

Tonight, the former London mayor will appear in a live BBC TV debate before an audience of 6,000 people at Wembley Arena. Facing him arguing for Remain will be Ruth Davidson, the Scottish Conservative leader.

Party sources have suggested Ms Davidson would consider breaking the Scottish Tories off from the UK party were Mr Johnson ever to become its leader. The Scots Tory leader has reportedly suggested the Uxbridge MP has the same “brazen chauvinistic style” as former SNP leader Alex Salmond.

Mr Johnson dismissed Chancellor George Osborne's claims that the UK Government had not made plans for the possibility of a Leave vote on June 23.

"It may be that he personally doesn't have a plan but I actually find it incredible with the polls, where they are, that the British Government, the Cabinet Secretary, the whole of the civil service is not actively working on it," he said.

"I'm sure they are working on some sensible plans."

Mr Farage's "Breaking Point" poster showing a column of non-white migrants, who had arrived in Europe last year, has been widely criticised by figures on both sides of the referendum debate with Vote Leave's Michael Gove saying he "shuddered" when he saw it.

But a member of the public confronted Mr Johnson over the ad on an LBC phone-in, accusing Vote Leave of being content to reap the votes generated by Mr Farage's "scurrilous, xenophobic" campaign while disowning him in public.

The Conservative backbencher insisted he was offering a "positive" vision on immigration, including an amnesty for illegal migrants who had stayed more than 12 years in the UK.

He said the poster had "xenophobic undertones" and insisted: "We have nothing to do with that campaign. The official Vote Leave campaign was given the designation by the Electoral Commission. We have absolutely nothing to do with any other campaign. We are fighting our campaign. My campaign is based on fairness.

"On the poster, I didn't like it. It seemed to be saying that these were bad people coming to our country. That seemed to be the message. I felt profoundly unhappy with it.

"When I was first campaigning to be mayor of London about nine years ago, I remember people saying to me that I was going to get the votes of the far right, and I said I didn't want their votes. I don't want them," insisted Mr Johnson.

he MP broke into the Latin of poet Virgil to insist that he wanted "not this aid and not these defenders", telling interviewer Nick Ferrari: "Non tali auxilio, nec defensoribus istis, as we say on the Vote Leave campaign."

He declared: "My vision is a positive vision. It's only if you take back control of immigration that you can actually neutralise extremism. One of the reasons why you are seeing a rise in extremism and far right politics in Europe is because of people's feeling that they are not being consulted about immigration and about the numbers, and the politicians who are meant to be in charge can't control it."

Mr Johnson repeatedly refused to say whether he had spoken to Mr Farage during the past few weeks, saying only: "I want to talk about our campaign."

Asked what he would say to Ukip backers, he replied: "I hope that everybody will support us and vote Leave to take back control