John Major accuses Leave camp of deceit as he brands Boris Johnson a "court jester"

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Sir John also took aim at leading Brexiter Boris Johnson, describing him as a “court jester” and said the promises of a leave vote leading to hundreds of millions of pounds more being spent on the NHS were “fatuous” and a “deceit".

In an extraordinary blue on blue attack, he said the health service would be as safe in the hands of Mr Johnson, Justice Secretary Michael Gove and former cabinet minister Iain Duncan Smith as a "pet hamster would be with a hungry python"; he accused Mr Gove of wanting to privatise the NHS, Mr Johnson of wanting to charge people to use it and Mr Duncan Smith of wanting a social insurance system.

The former prime minister also warned that if the Out campaign won, then the “Scots may hold another referendum; we might end up with Britain out of the EU and Scotland out of the UK”.

On Thursday, Nicola Sturgeon will push Scotland front and centre of the UK debate when she appears in a live ITV head-to-head, expected to be opposite Mr Johnson, who will face an all-female line-up arguing for Remain. On Tuesday, Mr Cameron will appear on the same platform with Ukip’s Nigel Farage in an ITV live question and answer session albeit not at the same time.

In response to Sir John’s blistering attack, Matthew Elliott, Vote Leave chief executive accused him of looking "slightly mad" while Brexiter Andrea Leadsom, the UK energy minister, said: “He’s obviously decided playing the man is going to be the better tactic for the Remain side.”

Appearing on BBC’s Marr Show, the former Tory premier appeared to be barely able to contain his fury at the Leave campaign and its tactics.

In a furious fusillade of criticism, the former Conservative leader hit out at Leave’s “inaccurate” and "deceitful" claims, directly accusing Brexiters of "misleading" the public.

While he said he was not personalising the issue, he took aim at Mr Johnson, dubbing him a "court jester", who was dividing the Conservative Party and who would not have the loyalty of Tory MPs if he became party leader.

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"Firstly on the economy and what would happen if we actually left, the Leave campaign have said absolutely nothing to the British people and what they have said about leaving is fundamentally dishonest and it's dishonest about the cost of Europe.

"And on the subject that they have veered towards, having lost the economic argument, of immigration, their campaign is verging on the squalid."

Sir John added: "I am angry at the way the British people are being misled; this is much more important than a general election, this is going to affect people, their livelihoods, their future, for a very long time to come and if they are given honest straightforward facts and they decide to leave, then that is the decision the British people take.

"But if they decide to leave on the basis of inaccurate information, inaccurate information known to be inaccurate, then I regard that as deceitful."

Later on the same programme, Mr Johnson dismissed Sir John's stinging assessment, insisting it was "not true" that the Leave camp's claims about Britain sending £350 million a week to Brussels was "fictitious" or the campaign was "squalid".

Asked if he believed the attacks against him were part of a plot to "take him out", the former London mayor, told presenter Andrew Marr: "Whether it is or not, I'm rather with John McDonnell this morning who says that there is too much of this blue on blue action and what he wants to hear is the arguments and that's where I am."

Mr Johnson said it was "absolute nonsense" that he was backing Brexit out of personal leadership ambitions.

"Obviously, there is going to be a temptation by one side or the other to try to turn it into a personality-driven conversation. My view about the EU has changed but that is because the EU has changed out of all recognition," he declared.

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The former London mayor has been the subject of a number of personal attacks from pro-EU Tory grandees.

Michael Heseltine, the former deputy prime minister, accused him of irresponsible behaviour and accused him of making “preposterous, obscene political remarks”, and Ken Clarke, the ex-chancellor, said the Uxbridge MP was not serious and just a nicer version of Donald Trump.

In his BBC interview, Mr Johnson also claimed the UK's population could rise "inexorably", potentially as high as 80m.

The Conservative MP failed to reject a Vote Leave poster claiming Mr Cameron could not be trusted on immigration, saying it was "frustrating" that the UK Government had failed to meet its pledge to reduce migration to the tens of thousands.

He claimed the PM "didn't get a sausage" from his renegotiations on Britain's relationship with Brussels.

Questioned whether or not he would row back from the comparison he made between Adolf Hitler and the EU, Mr Johnson simply said: "I don't write the headlines."

The London MP, who has Turkish heritage, defended the Leave campaign's claims about Turkey's future membership of the EU.

"Frankly, I don't mind whether Turkey joins the EU, provided the UK leaves the EU," he stressed.

Pressed on his previous support for Turkish accession, Mr Johnson insisted "that was back in the days when some of us thought that widening the EU would not mean this federalising, centralising, deepening process that we have seen". The EU, he insisted, had “changed out of all recognition”.

The Tory backbencher confirmed the Out camp’s view that Britain would not be part of the Single Market after Brexit, describing the impact on the economy as hockey stick-shaped.

Meantime, Mr Gove made clear Brexit would allow the UK Government to reduce net migration to the tens of thousands, the PM’s famous “no ifs, not buts” promise he has been unable to keep; net annual migration is now more than 300,000. However, the Scot was unable to put a timescale on it.

The Secretary of State suggested that even if voters backed Brexit in the June 23 referendum, Britain would still be part of the bloc by 2020.

He told ITV's Peston on Sunday: "We wouldn't have left the European Union by the end of this Parliament but we would in due course bring it down to tens of thousands.

"I wouldn't set a time-limit for it but the ambition would be to bring it down to tens of thousands."

Put to him that it would mean reducing both EU and non-EU immigration, Mr Gove said: "Yes.

"I absolutely don't think [that it would damage Britain's prosperity] because at the moment uncontrolled numbers coming in here only depress wages for working people.

"It's also the case that they put a considerable strain on public services, on housing, on the National Health Service, and of course on school places.

"We grew very successfully in the 1980s and the 1990s with immigration in the tens of thousands," he added.

In a weekend newspaper interview, Mr Cameron vowed to make Leave campaigners like Mr Johnson "pay" for their claims about Britain's economic prospects outside the EU.

Pledges made by London's former mayor and Mr Gove that the UK would strike up a series of swift and lucrative international trade deals if voters backed Brexit, were "nonsense on stilts", the PM said.