Nicola Sturgeon has said she cannot give Ed Miliband a guarantee that there will not be a second independence referendum during the lifetime of the next parliament because such a decision would be taken by the Scottish people.

The First Minister said she was "not planning" for another vote on independence but she did not have the right to categorically rule one out.

Ms Sturgeon was appearing on BBC1's Andrew Marr Show when she was questioned about a possible deal between Labour and the SNP after the General Election.

She confirmed she would lead any post-election discussions with the Labour leader.

Asked if she could give Mr Miliband a guarantee of no referendum in return for a Westminster deal, Ms Sturgeon said: "I have made very clear that if you vote SNP in this election, that is not a vote for independence, nor is it a vote for another referendum.

"I'm not planning another referendum. Why do I fall short of categorically ruling it out? Because I don't think as a single politician I have got a right to do that.

"Whether there is another referendum, and whether Scotland becomes independent is not a matter for me to decide. It is a matter for the Scottish people to decide."

Ms Sturgeon rejected the view that the SNP would attempt to cause disruption at Westminster to further its goal of independence.

She said the party wanted to work for "progressive change" across the UK.

"I think there are many people in Labour's ranks, including on their backbenches now, and perhaps in future, who would have the same view as me on many of these issues," she said.

"There is an opportunity to build progressive alliances for progressive policies. It is a real rather than a pretend alternative to austerity.

"I've got to persuade people that the SNP in the House of Commons after the election will not be any kind of disruptive force. We want to be constructive, to get better politics coming out of the Westminster system.

"As long as Scotland remains part of the Westminster system, it matters to people that we get good decisions out of that system, and I want the SNP to play a positive part in improving politics at Westminster for people right across the UK."

Speaking on BBC Radio 5 Live, Alex Salmond said the SNP had received "thousands of applications from people in England who want to join the SNP" following Ms Sturgeon's performance in the televised leaders' debates.

He said audiences "seemed quite enamoured by the prospect of Nicola Sturgeon's politics having an influence in the House of Commons".

"You have really got to divide the attitudes of the Westminster political establishment from the people of England," he said.

"The people of England don't think like Westminster politicians."

Asked about concerns over a Labour minority government supported by the SNP in an informal arrangement, Mr Salmond said: "The voters, the people, the real people ... they are not evincing that concern. The people who are evincing that concern are Westminster establishment politicians."

Commenting on whether the SNP would have no choice but to support Labour, or face accusations of allowing the Tories back into power, he said: "I have had experience of this exact situation ... that is the Scottish Parliament between 2007 and 2011 when I led a minority administration.

"As a minority government I had to face my responsibilities. I didn't disregard the views of anyone in that parliament. I couldn't, because I didn't have a majority.

"That is exactly what it would be like for Ed Miliband, or any other person in that position. They have to accept the verdict of the electorate, and act responsibly and democratically."

The former First Minister said no politician should "arrogantly dismiss the electoral arithmetic" and they are "foolish" to do so.

"That attitude, that posturing, makes them look rather out of touch with reality," he said.

Mr Salmond reiterated Ms Sturgeon's view that the question of an independence referendum was not an issue for this election.

"As Nicola has pointed out very strongly, this is a matter for the people of Scotland," he said.

Responding to Ms Sturgeon's comments, Scottish Labour's deputy leader Kezia Dugdale said: "The referendum just 213 days ago was supposed to be a once-in-a-generation deal.

"Nicola Sturgeon's refusal to rule out a second referendum in the lifetime of the next parliament, let alone the generation she promised the people of Scotland, makes it clear the SNP have gone back on their word.

"In every UK and Scottish Parliament manifesto the SNP has produced since 1999 they have backed a referendum. Tomorrow the SNP must address this issue again.

"It's their last chance before the election to rule out another referendum for a generation like Scots were promised just a few months ago."

Meanwhile, SNP deputy leader Stewart Hosie said Labour had questions to answer on where it would make cuts.

The party's manifesto, published last week, stated there will need to be "spending reductions, outside of the protected areas of health, education and international development".

Mr Hosie said Ms Dugdale had "dodged" questions on the cuts during a television interview.

He said: "Scottish Labour must come clean and let the people of Scotland know where their cuts axe will fall. While their manifesto clearly spells out they plan cuts to the Scottish budget, today we again saw the party duck and dive as their deputy leader dodged questioning on where these cuts would be made.

"This is hugely embarrassing for Scottish Labour - and the people of Scotland are waiting for answers. With no detail on cuts, the rest of their manifesto pledges are not worth the paper they are written on."