Alex Salmond has dismissed a Westminster pledge to enhance Scotland's powers after a No vote as a "last minute desperate offer of nothing".

David Cameron, Ed Miliband and Nick Clegg made the vow in a signed letter which appears on the front page of the Daily Record newspaper.

The First Minister insisted the promise of extensive new powers for the Scottish Parliament would not dent the Yes campaign and raised questions about how binding the pledge is.

He told BBC Radio Scotland's Good Morning Scotland: "This so-called vow that has been in the Daily Record, I suspect it's been called a vow because the last time one of these leaders made a pledge and signed the pledge was the Deputy Prime Minister Nick Clegg when he signed a pledge that he wouldn't have tuition fees and then promptly put them up to £9,000 for English students in England.

"It's a classic example of how this last minute desperate offer of nothing is not going to dissuade people in Scotland from the huge opportunity of taking Scotland's future into Scotland's hands this coming Thursday."

Labour's Douglas Alexander said the pledge sets out a vision that can unite Scotland.

The shadow foreign secretary told BBC Breakfast: "Here in Scotland, we have been talking about these powers for many months.

"What we're saying today on the front page of the Daily Record is that we can have the best of both worlds. We can have a stronger Scottish Parliament but with the strength, stability and security of the United Kingdom.

"My sense is that in the closing days, the final hours of this referendum campaign, that vow that we can have faster, safer, better change is actually a vision around which Scotland can unite."

Mr Alexander added: "I think the Yes campaign are struggling. They had an avalanche of facts engulf their assertions last week, when it was announced every major Scottish bank would move their registered office to London.

"We've had a company like Standard Life confirming that it would move operations south. The economic risks suddenly became very real last week.

"At the same time, we're offering what I believe most of us here in Scotland want - faster, safer and better change."

In today's letter, the party leaders say they agree that ''the UK exists to ensure opportunity and security for all by sharing our resources equitably across all four nations''.

In today's letter, the party leaders say they agree that ''the UK exists to ensure opportunity and security for all by sharing our resources equitably across all four nations''.

They state that the final say on funding for the NHS will be a matter for the Scottish Government "because of the continuation of the Barnett allocation for resources, and the powers of the Scottish Parliament to raise revenue".

Mr Miliband is on the campaign trail and will tell voters that a No vote is a vote for change and not the status quo.

The Labour leader will say: ''The will of the people of Scotland for economic and political change has been heard and we will deliver.

''Change is coming, with more powers on tax and welfare for the Scottish Parliament.''

Liberal Democrat Highland MP Charles Kennedy will take his party's campaign to Glasgow to launch a new poster van highlighting the positive case for Scotland staying in the UK.

He will be joined by Scottish Liberal Democrat leader Willie Rennie and Chief Secretary to the Treasury Danny Alexander.

Mr Kennedy will say: ''Together, our family of nations has achieved great things. In so many ways we have built the best.

''In the NHS we have the best health service in the world. We are the world's second largest aid donor, helping the planet's poorest. And in the BBC we have the world's best broadcaster too.

''We've built these things together. And I don't believe that we should walk away from them.''

Elsewhere, Green Yes, the Scottish Green Party's campaign for a Yes vote in the referendum, will be campaigning in the Leith area of Edinburgh.

The Scottish Young Greens will be joined by Green MSPs Patrick Harvie and Alison Johnstone to welcome activists from across Europe to the city.

Mr Harvie said: ''In recent weeks, Scottish Greens have been receiving messages of support from colleagues around the world as we campaign for a Yes vote.

"Our friends see the chance we have of achieving a fairer, greener future for Scotland, but also the chance for the UK to renew itself as a result.''