Nicola Sturgeon has insisted that the General Election is “not about independence” for the SNP, while Jim Murphy has argued that the First Minister will use a good result for her party to push for another referendum.
The party leaders’ messages clashed as they moved in to the final days of the campaign.
Ms Sturgeon will deliver a speech in Glasgow today, where she will tell voters that the SNP stands ready to help implement “progressive policies” across the UK.
She will call for all Scots to support the party, regardless of whether they voted Yes on No in the September independence referendum.
But Mr Murphy, also on the campaign trail in Glasgow, will argue that the SNP would use significant gains at Westminster as a launch pad towards a second vote on leaving the UK.
Ms Sturgeon is expected to say: “For me and my party, making Scotland stronger at Westminster – and helping to deliver progressive politics for the benefit of every part of the UK – are mutually supportive.
“They are different sides of the same coin – and we can all benefit together.
“If Scotland is stronger at Westminster with a team of SNP MPs, that influence will be used to deliver a fairer society – north and south of the border.
“As I have made very clear, this election is not about independence or about another referendum.
“It is about giving Scotland real power at Westminster and about making sure that the voices of families, communities and individuals the length and breadth of Scotland – those who voted Yes and those who voted No last year – are listened to.”
A recent opinion poll showed support for the SNP above 50%, suggesting the party could win dozens of seats on May 7.
Ms Sturgeon will reject suggestions that the SNP should not exert influence over a Westminster government.
“It is outrageous to hear representatives of the UK establishment, past and present, imply that some voices – and some votes – should be worth less than others,” she will say.
“Make no mistake, the people of Scotland can be heard – loud and clear – at this election.
“Their votes will be counted and their votes will matter.
“For as long as Scotland remains part of the Westminster system, that means our voice – and our votes – must have equal weight.”
Mr Murphy will highlight Ms Sturgeon’s refusal to rule out including another referendum in the SNP’s manifesto for the 2016 Scottish Parliament elections during a visit to a day centre to meet pensioners.
Scottish Labour leader Jim Murphy said: “The next Labour Government will work flat out every single day to make life fairer for working class Scots. That’s what will guide us in everything we do.
“The contrast with the SNP, who are planning another referendum as soon as they can get one, couldn’t be greater.
“The priorities of Scots going about their daily lives are paying the bills and making sure their families get on in life. A Labour Government will help working families do exactly that.
“The SNP want to spend all their time and energy working for another divisive and time consuming referendum. No pensioner living in poverty will be helped by another referendum. No family will see their wages go further with another vote on independence.”
He will add: “The way to get a Labour Government that won’t seek to divide Scotland with another referendum is to vote for Labour. A vote for anyone other than Labour risks the Tories being the largest party across the UK and David Cameron walking back into Downing Street. For the sake of working class families in Scotland we need to do everything we can to avoid that.”
Elsewhere on the campaign trail, Conservative leader Ruth Davidson will focus on defence during a visit to Tayside.
Speaking ahead of the visit, she said: “The Conservatives have pledged to do what it takes to ensure that our defences remain strong over the coming years and that our troops have what it takes to do their job.
“No more sending our armed forces into conflict without the proper kit, as we saw in wars past.
“We will protect spending on aid so that we can continue to help those struck by disaster or poverty.
“And we will renew our Trident submarines so that Britain is protected in an uncertain world.”
Scottish Liberal Democrat leader Willie Rennie meanwhile will set out the choice facing voters in eleven Lib Dem seats to a team of footballers at World of Football in Edinburgh.
He is expected to use the event to criticise SNP borrowing plans and Tory plans for further cuts.