The leaders of the pro-Union parties will today abandon Westminster to launch a desperate 11th-hour bid to turn the referendum campaign back in the No campaign's favour and save the United Kingdom.

The arrival of Tory Prime Minister David Cameron, his Liberal Democrat deputy Nick Clegg and Labour's Ed Miliband in Scotland takes place 24 hours after their counterparts in Scotland presented a united front on the promise of more additional powers for Holyrood on tax, welfare and spending with a fast-track timetable to deliver them.

But Alex Salmond, campaigning in Edinburgh, poured scorn on the UK party leaders, saying their Scottish trip was borne out of blind panic and showed the No camp to be in complete disarray.

The First Minister said the visit would simply play into the hands of the Yes campaign, adding: "The No campaign are making blunder after blunder but this is by far the biggest yet."

In Glasgow, Former Labour Prime Minister Gordon Brown, who has taken a central role in the No campaign, was yesterday close to tears as he talked about the loving care his prematurely born baby daughter Jennifer received in NHS hospitals before her death in 2002 from a brain haemorrhage, in further evidence the health service has become a key independence battleground.

Meanwhile, there were claims asset managers, investors and pension savers are moving billions of pounds out of Scotland. In the wake of the pound's slump against the dollar and falling stock prices of Scottish firms on Monday, Multree Investor Services said it had already moved hundreds of millions of pounds for its clients. Chief executive Chris Fisher said: "Other financial services companies are doing it as well."

In London, Buckingham Palace intervened to make clear any suggestion the Queen wanted to influence the vote was "categorically wrong" after ­speculation she was concerned about the prospect of independence.

After No 10 had said the Prime Minister would not travel to Scotland this week, a change of mind was agreed on Monday in a meeting with Mr Miliband. A Whitehall insider said it was also to maintain momentum from Mr Brown's announcement of a plan of action for enhanced devolution.

Mr Cameron said the right place to be "wasn't Westminster at Prime Minister's Questions, it is being in Scotland, listening to people, talking to people".

In a plea to Scottish voters, he said: "The United Kingdom is a precious and special country. That is what is at stake. So let no-one in Scotland be in any doubt: we desperately want you to stay; we do not want this family of nations to be ripped apart.

"Across England, Northern Ireland and Wales, our fear over what we stand to lose is matched only by our passion for what can be achieved if we stay together.

"If we pull together, we can keep on building a better future for our children. We can make sure our destiny matches our history, because there really will be no second chances. If the UK breaks apart, it breaks apart forever."

Mr Cameron will be in eastern Scotland, Mr Clegg in the Borders and Mr Miliband in Glasgow. Prime Minister's Questions will be taken by William Hague, the Commons Leader, and Harriet Harman, the Deputy Labour leader.

A senior Coalition source said that, while there were no plans, it was possible the three UK party leaders could make a second synchronised visit to Scotland next week too.

In Edinburgh, all three Scottish party leaders endorsed the Coalition's Plan of Action: a consensus on extra powers by the end of October; a White Paper by St Andrew's Day; draft legislation by Burns' Night, and implementation soon after the General Election.

Johann Lamont, the Scottish Labour leader, said this meant whoever won next May's poll "we know there will be more powers for the Scottish Parliament; that is an important commitment from all of us".

Asked if Mr Cameron was intent on delivering devo-max, his spokesman said he had not seen a single widely accepted description of this but stressed what was on offer was "fiscal autonomy, taxation, welfare, spending; that is a very significant further devolution".

Mr Salmond said: "Repackaging, after 48 hours of total confusion, exactly the same packages that were on offer in the spring. All that tells us is the No campaign is both in fundamental disarray and terminal decline."

Meanwhile, Mark Carney, governor of the Bank of England, told the TUC in Liverpool a currency union between an independent Scotland and the UK would be "incompatible with sovereignty".