David Cameron has made an ­impassioned plea to Scots to reject ­independence as Gordon Brown predicted that a series of new guarantees for Scotland would secure a No vote on Thursday.

In an emotional speech in Aberdeen, the Prime Minister begged voters not to leave the Union, telling them "head, heart and soul" he did not want them to go.

The Tory leader said: "I speak for millions of people across England, Wales and Northern Ireland - and many in Scotland, too, who would be utterly heartbroken by the break-up of the United Kingdom. Utterly heartbroken to wake up on Friday morning to the end of the country we love."

He acknowledged his unpopularity in the campaign, saying "if you don't like me, I won't be here forever," and warned that independence was permanent.

Alongside the pleas there were ­warnings that half of Scots mortgages would be held in a foreign country and that family and friends would become "foreigners" if Scots back a Yes vote.

The Conservative leader also emphasised his pledge that "a vote for No means real change" for Scotland.

Speaking in Edinburgh at the same time, Mr Brown called on the pro-Union parties to offer "locked in" guarantees to Scots.

These would include a pledge that the ­Scottish Parliament could never be abolished by Westminster and the continuation of the controversial Barnett formula, which allocates money to Scotland. These, he suggested, would allow future Holyrood ministers to spend more on the NHS.

And last night it emerged Mr Cameron, Liberal Democrat Deputy Prime Minister Nick Clegg and Labour leader Ed Miliband have signed a pledge promising to implement Mr Brown's proposals. They said in a joint declaration: "We believe that the arguments that so powerfully make the case for staying together in the UK should underpin our future ... we will honour those principles and values not only before the referendum but after."

A Scottish Conservative spokesman said the three pro-Union parties were 100 per cent behind Mr Brown's "sensible" proposals.

But Yes Scotland's Blair Jenkins warned voters: "Instead of believing the word of a Tory prime minister on very few more powers, the people of Scotland can get all the powers we need to build a better, fairer country by believing in ourselves and voting Yes."

With just two days to go before voters go to the polls, last night 5,000 people gathered in Trafalgar Square in London to tell Scottish voters they wanted them to stay.

Bob Geldof told the event that many Scottish voters were not alone, saying: "We're all f****** fed up with Westminster".

The White House weighed in, saying Washington would respect Friday's outcome but would prefer the United Kingdom to remain "strong, robust and united".

There were also warnings that the cost of borrowing to fund public spending on schools, hospitals and roads would go up in an independent Scotland.

Earlier, Mr Cameron had warned Scots a Yes vote would "not be a trial separation; it would be a painful divorce".

Mr Jenkins said: "David Cameron's speech was the same litany of empty threats and empty promises we have come to expect from the No campaign - and he is the Prime Minister who has been orchestrating the campaign of ridiculous scaremongering being directed against Scotland.

"A Yes vote is Scotland's one ­opportunity to ensure we get the job-creating powers we need to build a more prosperous economy and fairer society - and the financial powers we need to protect our health service. And only by voting Yes will Scotland always get the governments we vote for - and never again Tory governments imposed by Westminster, presiding over the scandal of a 400 per cent increase in the use of food banks while wasting £100 billion on a new generation of Trident nuclear weapons dumped on the Clyde."

Mr Brown predicted that his three guarantees, which he said would lock in change, would ensure independence is rejected on Thursday by winning over recent Yes converts.

Mr Brown said he sensed that people want change than can unite Scotland, but not necessarily by voting Yes. He said: "People want change... after a lengthy and often acrimonious debate, I sense that people want change that can unite Scotland, rather than divide Scotland."

He added: "They want to know that a No vote does not mean no change and instead seek guarantees of change locked in and clear assurances that from September 19 the pace of change will not stall but speed up."

"They want a promise of change they can trust - without the risks and uncertainties of an irreversible separation. I believe they are saying to us: 'Give us the guarantees of change, and with these guarantees we can vote for a strong Scottish Parliament within the UK'."

Last night Alex Salmond said he was "delighted" to visit his home town, Linlithgow, where he met his childhood friend Ronnie Bambury - and saw that the occupants of his childhood home had Yes signs in their window.