NICOLA Sturgeon has revealed how the SNP will seek to split Labour to impose SNP policy on a minority Ed Miliband government after the election.

The SNP leader admitted she would need Labour rebels to join her "progressive alliance" to win concessions from a Labour government, if Mr Miliband enters Downing Street but cannot command a Commons majority.

In an exclusive interview with The Herald, Ms Sturgeon also hinted she will not fight next year's Holyrood election on a clear cut pledge to hold a second independence referendum.

She denied she would come under irresistible pressure from within in her party to include the promise in her 2016 manifesto, insisting SNP members were a "pragmatic bunch" who understood that the country would not be rushed into a re-run of last year's historic vote.

Polls suggest the SNP will win upwards of 50 seats in Scotland and take their place in a House of Commons where neither the Conservatives nor Labour command an outright majority.

In that scenario, Ms Sturgeon has said her MPs would vote against a Conservative Queen's Speech in a bid to "lock out" a Tory government and allow Mr Miliband to become Prime Minister.

But she admitted SNP policies could only be carried if Labour rebels also backed them.

She said: "If we are in a minority Labour government situation, with a big team of SNP MPs, what we will be doing is trying to build alliances on an issue by issue basis.

"That will be trying to win support from Labour backbenchers as well as from Greens, if there are Greens and from Plaid Cymru MPs."

In East Anglia today, David Cameron will launch the first ever Conservative manifesto for England, making clear, if he wins power, he intends to introduce English Votes for English Laws within 100 days and an English income tax rate by the Budget of March 2016.

In a campaign speech, the Prime Minister will deny the Labour charge that he has become an English Nationalist and insist how he is a Unionist "through and through".

Ms Sturgeon says her first priority will be to secure support for her plan to raise public spending by 0.5 per cent per year over the next parliament.

She said: "I suspect there will be a lot of people on Labour's back benches who think that is the right thing to do.

"I think there will be a lot of opportunity, if there is a minority Labour government, to shift Labour into that position.

"That's part of the building alliances. In a minority parliament you build alliances to shift the position of the government.

"And the beauty of the Fixed Term Parliaments Act in the House of Commons is you can change the direction of a government, you can defeat the government on particular issues, without brining down the government."

Ms Sturgeon's appeal to Labour backbenchers was undermined by the independent IFS think tank, which yesterday concluded that overall spending was likely to be lower under the SNP's plans than Labour's by 2019/20, based on the two parties' manifestos.

Her comments reinforced her pledge to be a "constructive" force at Westminster but also illustrated the limits to the SNP's possible influence, even it secures the overwhelming majority of Scotland's 59 seats.

The Conservatives have claimed a minority Labour government would be dragged to the left as it was forced to "dance to the SNP's tune".

But Ms Sturgeon said: "I want us to go into this to effect positive change.

"It is not a case of us going to disrupt or bring down government at the first opportunity, or bring down a budget, we're trying to use whatever influence people here give us positively to get the kind of changes we are arguing for."

The First Minister said victory for the SNP in Scotland on May 7 would not give her a mandate for a second independence referendum.

She has warned previously that David Cameron's proposed in/out referendum on the UK's EU membership could trigger a second independence vote.

However, she talked down the prospect of making a clear cut referendum promise ahead of the next Holyrood election.

She said she was "not at this moment planning another referendum" and denied she would be unable to resist pressure from her party's 100,000 members to promise a re-run after 2016.

In a message designed to dampen expectations among the party faithful, she said: "My experience of the members, and I can't claim to have spoken to all of them but I have spoken to a significant number, is they are a very pragmatic bunch, who understand the realities of politics.

"They also understand this democratic point: That Scotland will only be independent when a majority of people want Scotland to be independent.

"No matter how much we might want to rush that process the Scottish people will not allow it to be rushed.

"My experience of the new members and our existing members is that they understand that."