Political parties focus on economic policy
The Liberal Democrats have claimed full tax powers for Scotland would leave a black hole in the public finances.
The claim has been firmly rebutted by the SNP.
It came as Scottish Labour urged political policies to "focus on fairness" and the Conservatives said the UK economy was already showing signs of improvement.
The parties' views on the economy anticipated the official start of the General Election campaign on Monday.
The Liberal Democrat claim of a potential shortfall in Scottish public spending was explained by Danny Alexander, chief secretary to the Treasury in the UK coalition government.
Using new Treasury figures, Mr Alexander said Scotland would be left with a £40bn funding gap by the end of the next Scottish Parliament.
He said: "That money could only be found by racking up taxes in Scotland or massive cuts for the NHS and other public services."
The SNP rejected Mr Alexander's analysis.
The party's deputy leader and Treasury spokesman Stewart Hosie said: "The only risk to Scotland's public finances and services are the cuts planned by all the Westminster parties.
"And the key to our long-term economic success and ability to invest in our public services is giving Scotland the economic tools needed to grow our economy and boost revenues.
"Electing a powerful group of SNP MPs in May will help stop a further wave of cuts and help us deliver those powers to Scotland."
Visiting a Glasgow food bank, Scottish Labour leader Jim Murphy has been outlining his party's policies on "fairness".
He said: "We've got to create a fairer country. It's immoral that in a country as rich as ours, tens of thousands of people are having to rely on charities like this to feed their children and feed themselves.
"We need to end the old Jobcentre Plus targets that are punishing people for no good reason and kicking them off benefits.
"We need higher wages. We need to abolish the bedroom tax. We just need fairer government."
The Conservatives have been stressing what they see as the successes of the past five years.
Scottish Conservative deputy leader Jackson Carlaw said: "We haven't got the economy recovered by any means yet.
"But we've set it on the path to recovery, with lower inflation, with more people in work, with the budget deficit reduced by 50%.
"By all of these things we've demonstrated that we have an economic plan for the country and it's one that we should stick with."
On Monday, the Westminster parliament is formally dissolved. Voters go to the polls on Thursday 7 May.