Tory meltdown as 66 MPs stage open revolt against George Osborne's proposed Brexit Budget

His warning comes against a backdrop of shifting political landscapes in Scotland after shock TNS poll showed a majority - 53 per cent to 47 per cent - are now ready to back leaving the EU next Thursday.

Read more: How Brexit could open up new constituency of support for independence among middle-class Scots

Nicola Sturgeon was also accused of scaremongering after she warned that Brexit would lead to a more right-wing Conservative government as leaders of the Leave camp seized power from Mr Cameron.

Former SNP deputy leader Jim Sillars said the First Minister had "fallen from her own high standards" by "deploying the whiplash of fear" following her claims that Scotland would be in the firing line as the new Tory government axed workers' rights and cut public spending.

But on the campaign trail in Kent and flanked by his Labour predecessor Lord Darling, Chancellor George Osborne suggested the economic impact of Brexit would elicit major tax hikes and public spending cuts.

An emergency Budget would have to be launched, he said, that could involve £15bn of tax rises, including a 2p hike on the basic rate of income tax, and similar-sized cuts to public services spending, including a £2.5bn a year cut in the NHS.

But his former cabinet colleague Iain Duncan Smith, a leading Leave campaigner, called on Mr Osborne to “stop this nonsense” and said: “It is irresponsible to scare the public and to scare the markets.”

Later, appearing on a special EU edition of BBC TV's Question Time, Michael Gove, the Justice Secretary, became the most senior Conservative to oppose the chancellor's proposed Brexit Budget.

Read more: Think tank - Brexit would devastate workers' rights and consumer protections

Asked if he would support it, the Scot said: "No, because what we have heard from the Remain campaign throughout this whole referendum has been dire warnings of the terrible consequences of the British people just taking control of our own destiny.

"The truth is if we vote to Leave we will be in an economically stronger position. We will be able to take back some of the money that we currently give to the European Union and we can invest it in our priorities.”

In a joint statement the Tory Brexiters said the chancellor was threatening to renege on the Conservative manifesto commitments and effectively vowed to oust him from office, saying: “If he were to proceed with these proposals, the chancellor's position would become untenable...The chancellor risks doing damage to the British economy in his bid to win this political campaign."

Alex Salmond, the former First Minister, suggested senior Conservative Brexiters were now planning "a very British coup" to unseat David Cameron and Mr Osborne in the event of a Brexit vote.

The SNP MP for Gordon said the chancellor’s political career was “virtually over" regardless of the outcome of EU referendum because he had alienated scores of Tory MPs.

The chances of Mr Osborne getting his emergency Budget through looked doomed, however, after Labour leader Jeremy Corbyn made clear his party would not support any post-referendum austerity Budget. It is believed the SNP would take the same position.

Read more: How can the Tories recover from their publicly vented psycho-drama?

In a separate development, sources close to Nigel Farage suggested the Ukip leader had been approached by the Boris Johnson camp to sound him out over a possible job in a new Tory government led by the former London mayor, offering the MEP a place in the House of Lords to avoid having to fight a future Westminster by-election in Kent.

The escalation in Tory in-fighting came after Vote Leave set out its “roadmap” for Britain to take back control following a decision to quite the EU. It published details of five new Bills that should be introduced to enable the UK to set up its own trade deals and curb immigration. But critics suggested it appeared like the manifesto of a “Brexit government-in-waiting”.

Earlier, Prime Minister David Cameron told MPs it was “just plain common sense” to vote for Remain.

Answering a point from the SNP’s Angus Robertson that a decision to stay in the EU would protect jobs and public services, Mr Cameron replied: “For an economy such as Scotland’s, which is such a big exporting economy, there is no way we would get a better deal on the outside of the single market than we get on the inside, so if we left we would see our economy suffer, we would see jobs suffer and we would see people’s livelihoods suffer.”

Echoing that view, leading economist Brian Ashcroft argued that the Scottish economy would be placed in a "very difficult position" if it left the EU.

The emeritus professor of economics at Strathclyde University said he saw no “immediate argument” that Scotland would be better to become independent so it could try to get back into the EU.

"Frying pans and fires come to mind," he told the univerisity’s highly-regarded Fraser of Allander Institute. "There is no best scenario for Scotland in that scenario.”

He warned Scotland would suffer in terms of inward investment and international trade if the UK were to leave the EU.

Meanwhile, the Scottish entrepreneurial community has signalled its emphatic support for the UK to Remain part of the European Union.

Less than one-fifth of entrepreneurs have said they plan to vote Leave in the EU referendum, a survey by Glasgow-based Entrepreneurial Spark has found.

The survey also found that around 50 per cent of entrepreneurs fear the referendum will have an effect on business.

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