Nicola Sturgeon and Alex Salmond
SNP leader Nicola Sturgeon will unveil the party's manifesto in Edinburgh todayGetty

The SNP's "alternative to cuts" will be at the heart of the party's manifesto when Nicola Sturgeon unveils the "UK-wide" plan in Edinburgh today.

The manifesto is being launched the day before ballot packs start to arrive in people's homes on Tuesday for the start of the postal votes and will come after Sturgeon's appearance in the TV leaders' debates.

"Our message on Monday is that if people vote SNP they get SNP – and more importantly they get policies at Westminster on the economy, health, Trident and across all areas that deliver real change and real progress," a senior SNP campaign source said.

"This will be a manifesto for delivery UK-wide, with our alternative to cuts its centrepiece. For perhaps the first time, the SNP have proved our complete relevance to a Westminster general election."

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The policy document will commit SNP MPs to participate in votes on "major issues" in England and Wales, like a bill to restore the NHS in England to a "fully public, publicly accountable" service.

The manifesto will also outline the SNP's plan to cancel the renewal of the Trident nuclear deference system, which the party argues would free up £3bn ($4.4bn) of expenditure UK-wide per year.

The nationalists are set to win a swathe of seats from Labour in Scotland at the election and Sturgeon could be a king maker after May's vote.

The SNP leader has ruled out any deal with the Tories and has vowed to keep David Cameron out of Downing Street.

But Sturgeon has kept the door open for a deal between Labour and the SNP in Westminster after Ed Miliband ruled out a Coalition Government between the parties.

However, the Labour leader has failed to rule out a so called "confidence and supply" agreement, which would see the SNP voting in the Commons on a vote-by-vote basis.

The Tories have been able to exploit this potential deal between Miliband and Sturgeon and Conservative grandee Michael Fallon recently controversially claimed the Labour leader would not renew Trident in order to win Sturgeon's favour.

"Miliband stabbed his own brother in the back to become Labour leader. Now he is willing to stab the United Kingdom in the back to become prime minister," he wrote in The Times.

But the Labour leader hit back and argued that the Foreign Secretary had "demeaned himself and demeaned his office" by making such a personal attack.