Nicola Sturgeon keeps up pressure on Ed Miliband in bid to lock Tories out

Nicola Sturgeon, First Minister in Bute House 2

Nicola Sturgeon, the Scottish National party leader, has pressed Ed Miliband to accept the legitimacy of a large elected SNP team at Westminster, saying it would be unacceptable for unionist politicians who asked Scots to stay inside the UK on the basis that their voice mattered would then refuse to accept their legitimacy.

Related: Labour's Jim Murphy and Douglas Alexander set to lose seats to SNP - poll

Sturgeon was speaking after Ed Miliband again said he would not form a coalition with the SNP or let anyone but Labour write a Labour budget.

Speaking on Friday after he had rejected Sturgeon’s call to work together to lock the David Cameron and the Tories out of Downing Street, the Labour leader said: “The first budget of a Labour government is going to be written by a Labour government … It is not going to be written by Nicola Sturgeon or Alex Salmond or anybody else in the SNP. I could not have been clearer – how other parties vote on a Labour’s Queen’s speech frankly is a matter for them.

“I will never compromise our national security, I will never compromise our commitment to fiscal responsibility, I will never compromise on the nature of our United Kingdom. My message to Nicola Sturgeon is ‘thanks, but no thanks’. If you want a Labour government, my message is very simple: vote Labour.”

But his call came as another poll of Scottish marginal seats by Lord Ashcroft showed the SNP pulling even further ahead in Labour heartlands, placing the shadow foreign secretary Douglas Alexander and the Scottish Labour leader Jim Murphy in mortal danger.

Labour admitted in a statement: “There is no gloss that we can put on these polls.”

In a sign of the desperation of the unionist parties in Scotland, the Liberal Democrat leader Nick Clegg called for tactical voting to stop the SNP.

The former SNP leader Alex Salmond, who is standing for Westminster, admitted the degree of cooperation between Labour and the SNP may be piecemeal, rather than part of a loose pact. He said a loose, “confidence and supply” set-up was possible, but vote by vote was probable. “I think that’s a good way to express it.”

The SNP’s political difficulty is that it has ruled out putting the Tories back into power, so reducing its bargaining power with Labour. Sturgeon said: “We would never put the Tories into government,” adding that the SNP would help produce a better and bolder change from Labour.

She said: “In three weeks, if Labour and the SNP have more MPs than Cameron, is Miliband really going to say he won’t work with us?”

The narrowness of the polls are producing a huge range different hung parliament scenarios that are increasingly featuring in the thinking of senior politicians. But if the Tories were unable to form a government and Labourwas unwilling or unable to form a majority coalition with the Lib Dems, there is a possibility that Miliband might seek to govern on a day-by-day basis, testing SNP resolve.

The Tories’ difficulty is that they could come first in terms of seats, but are not able to form a majority coalition, leaving the SNP pivotal in deciding if Labour could govern.

Sturgeon told Sky News: “During the referendum campaign last year, we were told repeatedly by politicians that wanted us to vote no that Scotland was an integral part of the UK, that our voice mattered and our voice will be heard, so it strikes me as completely unacceptable for those politicians to turn round now and when Scotland choose to make its voice be heard by voting SNP to say your voice cannot be heard.”

She refused to rule out a second referendum on independence saying one was possible if circumstances such as UK withdrawal from the European Union occurred.

Cameron tried to paint a picture of chaos implicit in a hung parliament in which the SNP call the shots: “The fact is that Labour cannot win a majority on their own. They can only get into Downing Street with the support of the SNP. What is it that the SNP want? They want more borrowing, they want more taxes, they want more unlimited borrowing – they want all the things that got us into this mess in the first place.”

Powered by Guardian.co.ukThis article was written by Patrick Wintour Political editor, for theguardian.com on Friday 17th April 2015 20.39 Europe/Londonguardian.co.uk © Guardian News and Media Limited 2010