Westminster parties have rounded on the SNP insisting the party will cost the rest of the UK dearly and push for another independence referendum.
Former prime minister Gordon Brown sprung to the defence of Labour campaign co-ordinator Douglas Alexander, who is trailing 11 points behind the SNP according to a recent poll in his constituency, claiming his SNP opponent is preparing to "twist the arm" of Westminster for another referendum.
Meanwhile, the Conservatives launched a new poster in England featuring Alex Salmond picking a pocket with the slogan: "Don't let the SNP grab your cash."
The poster comes after Tory leader David Cameron was overheard jokingly describing Mr Salmond as a pickpocket on television.
But the SNP hit back insisting they will work to "bring an end to austerity", and that "this election is not about independence or another referendum".
Speaking in Elderslie, in Mr Alexander's Paisley and Renfrewshire South constituency, Mr Brown said: "There is an SNP candidate in this constituency. She says vote SNP, get SNP MPs at Westminster and we will twist their arms and get another referendum.
"Remember what the SNP used to say - the referendum was once in a generation, then it changed a little to once in a lifetime, then it was once every 15 years and now when you ask Ms Sturgeon about this her answers are all evasion. She cannot give a straight answer to the question.
"But does not the SNP candidate in this constituency tell the truth, that what they want is an SNP vote not to deliver social justice but to deliver the chaos and constitutional crisis at Westminster to as she said force a second referendum."
Mr Brown referred to a video featuring Paisley & Renfrewshire South SNP candidate Mhairi Black insisting the SNP will have to "twist the arm" of Westminster MPs to get them to agree to another referendum.
An SNP spokesman said: "The point that Mhairi Black was making was that if the people of Scotland do in the future decide there should be another referendum the Westminster establishment must not stand in their way."
Scottish Liberal Democrat leader Willie Rennie attacked the Conservative poster campaign in England.
He said: "I am no supporter of Alex Salmond or the SNP and am deeply concerned about their reckless borrowing and full fiscal autonomy plans which could derail the economy and dump debt on future generations.
"Yet this Conservative poster hits a new low. It does not take a brain surgeon to understand that they are generating and stirring English nationalism to resent the Scots to boost Tory votes.
"The Conservatives have effectively joined the SNP in trying to pull our country apart - all for a few votes in the general election."
But SNP leader Nicola Sturgeon thanked David Cameron's party for helping to raise the profile of the SNP.
In an interview with The Times, she said: "If this is the attention we get just from the SNP riding high in the polls, imagine how loud our voice would be if that was translated into seats. So in that respect I absolutely think it is not unhelpful."
A Conservative spokesman said: "By 'enormous influence', Nicola Sturgeon means higher taxes, higher spending, higher welfare bills and weaker defences.
"That's the ransom the SNP will demand from Ed Miliband in return for propping him up in government - and we'll all pay."
UK Liberal Democrat leader Nick Clegg ruled out any post-election deal with a Labour minority government propped up "on a life support system" by the SNP.
In an interview with the Financial Times, he said: "I totally rule out any arrangements with the SNP - in the same way I rule out any arrangements with Ukip - because there is no meeting point for me with one party that basically wants to pull our country to bits and another party that wants us to pull out of the EU."
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