Labour MPs in Scotland would be reduced from 41 to four while Lib Dems and Tories projected to lose all their seats

A new poll suggests the SNP will almost completely wipe out Labour in Scotland in May’s general election.

The poll for Ipsos Mori gives the Scottish National party a 28-point lead over Labour in Westminster voting intention, projecting 55 seats in Scotland for the nationalists and four for Labour. The Liberal Democrats would lose all their seats and the Tories would lose their one seat, held by the Scotland minister David Mundell.

Following the no vote in last September’s independence referendum, the SNP has seen a surge of support under its new leader, Nicola Sturgeon. A Survation poll for the Daily Record earlier in the week suggested signs of a recovery for Scottish Labour under Jim Murphy with the gap narrowing to 20 points, but it too indicated that the SNP would be in a powerful position in Westminster after May.

Sturgeon has ruled out any form of coalition with the Tories but has previously indicated her willingness to enter into talks with Labour. She told the BBC on Wednesday that she was “instinctively not too enthusiastic” about a formal coalition but tended towards a vote-by-vote deal.

Murphy has repeatedly said his party is not planning for a deal with the SNP, insisting that Labour will hold all of its 41 seats in Scotland at the coming election, but the UK Labour leader Ed Miliband refused to directly rule out post-election talks with the nationalists during a recent TV appearance.

Sturgeon said on Wednesday that SNP MPs were prepared to vote on English health legislation in order to protect the NHS in Scotland, in a striking policy shift that is expected to fuel Conservative calls for English laws for English votes.

Scotland’s first minister said it would represent “enlightened self-interest” for SNP MPs elected in May to vote on English health matters that have a direct impact on the Scottish budget.

She told the BBC: “If there was a vote in the House of Commons to repeal the privatisation of the health service that has been seen in England, we would vote for that because that would help to protect Scotland’s budget.”

The SNP position at Westminster has traditionally been not to vote on matters that do not have a direct impact on Scotland. By indicating some flexibility on votes on devolved matters such as health or education, Sturgeon places herself in a stronger position to support a minority Labour government should the circumstances arise.

On Tuesday George Osborne, the chancellor, told a meeting of the Commons Treasury select committee that if Labour did not rule out governing with the SNP, voters would not trust it to act in the interests of England when legislating for further Scottish devolution after the election. He said it would be unfair for the whole of the UK to have a future government that was “beholden on the Scottish nationalist votes” in the next parliament.

Sturgeon said: “If there are decisions taken to further privatise the NHS in England, and I don’t think anybody thinks the Tories are progressively privatising the health service in order to increase the public funding of the health service, so decisions are taken that reduce over time the public funding of the health service in England, then that has a direct knock-on effect to Scotland’s budget.”

Murphy responded: “The fact is the SNP is spending less on the NHS than even David Cameron. There is a way of getting a better health service, a way of getting more money for Scotland’s health service, and that is by voting for the Labour party.”

The draft Scotland bill based on the recommendations of the Smith commission, set up in the aftermath of the referendum to deliver more powers to the Scottish parliament, is due to be published on Thursday.