David Cameron has said that he will not resign if he loses the European Union referendum.

The Prime Minister’s vow came as one of his former colleagues insisted that the Queen would not back leaving the EU, because of fears over Scottish independence.

Ex-Lib Dem cabinet minister Sir Edward Davey rejected reports that the monarch supports Brexit.

"The Queen knows that if we vote to pull out of the EU, it's the surest way to destroy the United Kingdom, because Scotland will then vote to go independent,” he said.

Within hours Mr Cameron was forced to deny that he would stand down if he lost the vote.

Challenged by a Labour MP if he would resign “yes or not?”, the Tory leader replied: “No”.

In 2014 Mr Cameron said he had "thought about resigning" if he lost the independence referendum.

Mr Cameron's case for staying in the EU receives a boost today with new research by the University of Edinburgh.

Academics found that Europe is divided on whether or not, the UK could remain part of the single market if it were outside the EU.

Nearly half of Germans surveyed were in favour, but only a quarter of French respondents.

University of Edinburgh experts, along with the German think tank d|part, surveyed more than eight thousand people in six EU member states – Germany, France, Ireland, Poland, Sweden and Spain.

They also found little support for the UK having special privileges within the EU.

Most of those asked in every country said that any changes negotiated by the UK should apply to all EU member states.

The report's author Dr Jan Eichhorn: “The upcoming EU referendum provides an opportunity to engage with people’s views on the UK and their involvement in the EU across the whole continent. Our survey shows a willingness to reform the EU, but less so for an individual country to gain exceptional treatment.”

Meanwhile, the leader of the country's biggest trade union said that life outside the EU would be worse for workers, because they would be left to the "mercy" of the Conservative party.

Len McCluskey, the general secretary of Unite, said he was personally in favour of remaining - but stressed that the EU must return to its original mission of "solidarity and hope".

Speaking to an audience in London gathered by the German Ambassador, he said that a vote to stay in the EU should not be taken as support for the "finance first status quo" which had brought "misery" to ordinary people.

"I will not be voting for the EU which has sought to impose eye-watering austerity, at the expense of the ordinary citizen not the rich, but on Ireland, Greece, Spain, Portugal and elsewhere.

"I will not be voting for the EU which is seeking to stitch-up a pro-big business trade deal - TTIP - behind the backs of the people of Europe.

"Above all, I will not be voting for David Cameron's renegotiation package - a deal designed to protect the financial interests in the City of London which control the Conservative Party and to pander to anti-migrant and anti-welfare sentiment.

"It is disappointing to see how eager European governments were to accommodate him, in stark contrast to the reception given to premier Tsipras of Greece last year."

Labour leader Jeremy Corbyn also came under pressure as his party's candidate for London mayor suggested he should be more prominent on the issue.

Sadiq Khan has said that "without a doubt" he wanted Mr Corbyn to be more vocal in the campaign against Brexit.