The Bank of England warned that David Cameron's EU referendum could hurt the economy as a Tory MP broke ranks to call on the Prime Minister to resign immediately if he loses the vote.

Just hours after the Conservative leader appealed for calm within his own party, backbencher Nadine Dorries raised the stakes saying he would have to stand down if he failed to clinch victory at the ballot box.

Earlier, another eurosceptic Culture Secretary John Whittingdale bet television presenter Piers Morgan £1,000 that the Prime Minister would stay on.

But Ms Dorries said: "I would imagine and hope the first thing David Cameron would do is stand down as Prime Minister."

The row erupted as the most high-profile Tory in the Out campaign, Boris Johnson, appeared to accuse Mr Cameron of trying to “spread alarm”.

The London mayor hit out at almost 200 business leaders signed a letter organised by No 10 warning Brexit would “threaten jobs and put the economy at risk”.

Mr Johnson himself was challenged to a head-to-head on the issues by Former Scottish First Minister Alex Salmond, who predicted the battle between them would be "Scotland against England”.

The SNP also said it wanted to be involved in three EU referendum debates announced by the BBC, including a special edition of Question Time which will feature only "one senior advocate from each side", and an event in Glasgow.

Meanwhile, the governor of the Bank of England was forced to admit to MPs that the recent fall in the pound had been caused by uncertainties over the UK's future.

The bank also warned that fears of a Brexit could hurt the economy by hitting growth.

The Remain side, meanwhile, repeated its message that a Brexit would leave the UK worse off.

The Environment Secretary Liz Truss warned that it would put at risk food and farming exports worth £11bn.

Labour's Former Home Secretary Alan Johnson, meanwhile, said that two-thirds of manufacturing jobs were dependent on demand from Europe.

A separate row broke out over allegations of a 'cover up' after civil servants were banned from giving support to anti-EU ministers, because of the UK Government's pro-EU stance.

Pro-Brexit ministers will not have access to government documents or official assistance to help them make their case.

Commons Leader Chris Grayling warned the Government not to spend taxpayers’ money on just one side of the argument.

“I don’t think anybody is seriously expecting the Prime Minister to be sitting in Downing Street making the case all by himself in a room alone with no help," he said.

UKIP slammed what it said was an "appalling cover up".

Meanwhile, new evidence suggests Britons are more eurosceptic than at almost any point since 1992.

Professor John Curtice, who compiled the report for NatCen Social Research, warned that “Britain is as sceptical about Europe as it has ever been".

But, he added: "For most people on its own this scepticism is not enough to warrant leaving the EU."

Just days into the campaign, the internal war within the Tories prompted ex-leader William Hague to warn that the referendum must not cost the party the next general election.

Mr Cameron also tried to ease tensions calling for a "reasonable, civilised" battle, less than 24 hours after he gave what was interpreted a devastating attack on Mr Johnson.

The Prime Minister also appealed for more businesses to speak out for remaining in the EU.

He said: "Many businesses don't want to get involved in any political issue.

"But I would say to them, this is not like a general election, it's not about backing one team or another team.

"This is a decision that we are going to have to live with in Britain for decades to come.

"If you have a strong view, you should make it clear."

The Leave campaign pointed out that many firms, including supermarkets, had not signed the letter.