Former London mayor makes pledge to caller on LBC radio phone-in but says Britain has nothing to fear from leaving EU

Boris Johnson has said he will apologise on national television if Britain were to plunge into recession after a vote to leave the EU.

His promise came in response to a caller to radio station LBC, who asked the former mayor of London: “If we Brexit and we go into recession, would you have the political courage, to go on TV … and say sorry, I made it wrong and I apologise?”

Johnson promised he would apologise were the UK to slide into recession post-Brexit. “Of course I will,” he said. “I’m not certain what my political career holds anyway. This is far more important than any individual political career.

“I don’t think London has anything to fear from coming out of the EU, and neither does Britain. When has our country ever gone wrong by believing in ourselves?”

Financial experts and business leaders have ratcheted up warnings about the harm to the economy of a leave vote. In an article in the Guardian on Tuesday, the former currency speculator George Soros said if Britain leaves the EU “the value of the pound would decline precipitously”.

“I want people to know what the consequences of a vote to leave the EU would be before they cast their votes rather than afterward,” he wrote. “A vote to leave could see the week end with a Black Friday and serious consequences for ordinary people.”

One of Asia’s richest men, Li Ka-shing, whose portfolio includes mobile phone operator Three, Superdrug and Northumbrian Water, has also warned that a vote to leave would be “detrimental to the UK”.

Johnson played down the significance of Soros’s intervention, telling LBC on Tuesday: “The people I listen to are not people like George Soros, who speculate on market movements – that’s how he makes his money. I listen to people like Anthony Bamford of JCB, the biggest private manufacturer in this country.”

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Michael Gove, the justice secretary and leading leave campaigner, speaking earlier on BBC Radio 4’s Today programme, also denied Brexit would have as significant an impact as forecast by Soros and others. He had admitted over the weekend that there might be “bumps in the road” for the economy after a leave vote.

“If economic forecasters were as reliable as doctors or airline pilots, then everyone would be a billionaire,” Gove said. “The truth is that economic forecasters like George Soros have got things wrong in the past.

“The economic model that the European Union embodies is a job-destroying, misery inducing, unemployment-creating tragedy and if we vote to leave we can free ourselves from a sinking ship and also send Europe in a better, more progressive direction,” he said.

Speaking on LBC, Johnson dismissed claims by the chancellor, George Osborne, that the government had not made plans for the possibility of a leave vote, calling 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”.

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Downing Street, he said, had leant on business leaders to support a vote to remain, though he declined to be specific.

“I can’t tell you the pressure that Project Fear and remain put on senior business people not to articulate their views,” he said. “You will get a call from certain gentlemen … And they will say, ‘Look, you know, we want to continue to have contracts with you … there is an honours system as you know’, all this kind of thing. And that’s how it is. There is a bit of leaning on.”

Gove admitted he believed he would need to reconsider his role in government were Britain to vote to remain. “Of course, depending on what the result is on Friday, I will reflect and decide what is the best course for me,” he told Radio 4.