The parties have clashed over how to secure the economic recovery and prevent a repeat of the banking crisis.
Business Secretary Lord Mandelson, on the BBC's Daily Politics, said "painful choices" were needed to cut the deficit but Labour had a "credible" plan.
But his Tory counterpart Ken Clarke said Labour had "contributed" to the worst economic crisis in 60 years.
Lib Dem John Thurso urged bank reform, while the SNP's John Swinney said he would opposing "swingeing" cuts.
Setting out their agendas, the four men clashed over financial regulation, bank reform, the future of manufacturing and rules on foreign takeovers, among other issues.
Lord Mandelson insisted that Labour was still the "party of business" despite the opposition of more than 100 senior executives to their planned increase to National Insurance contributions.
'Growth plan'
He said "difficult decisions" would be needed on tax and spending to tackle the deficit, and the national insurance increase was part of a "credible" plan to reduce borrowing.
"Business wants a growth plan for Britain's future and that is what Labour is offering at this election," he said.
Asked whether the government should have done more to stop reckless lending in the lead-up to the financial crisis which began in 2008, Lord Mandelson said the "primary responsibility" for the situation lay with the banks.
"It is easy, with hindsight, to say we should have seen this coming, but nobody did".
But he said regulation of the City should have been more "intrusive", with the authorities looking "more closely" at banks' trading activities.
For the Conservatives, Mr Clarke said the government should take much of the blame for the banking crisis and the recession that followed.
"People have to be reminded that this is the worst economic crisis since the war," he said. "Gordon Brown contributed to it so he is no part of the solution".
Mr Clarke said he backed Labour's decision to nationalise Northern Rock - opposed at the time by the Conservative Party - but stressed he was not a shadow minister then and was free to disagree with his party over the issue.
But he criticised the government's handling of the crisis: "The regulatory system which Gordon Brown proudly put in place did not work. It was quite useless".
Mr Thurso said his party had been the first to warn about the dangers of the credit boom and that their plans to reform the banks must be taken seriously.
"It is a sector which nearly brought us to our knees and could do so again," he said.
"What we have to secure for the future is a banking sector which services commerce and industry and divorces the casino from the utility".
'Scottish lessons'
Mr Swinney, finance minister in the SNP-lead Scottish government, said the SNP would use its "bargaining power" in the event of a hung parliament to deliver benefits for Scotland.
He criticised what he said was a "London-based" consensus over spending cuts.
"The lesson from Scotland is that if there is a balanced Parliament, it can be made to work," he said. "We have to have a different agenda focused on growth in Scotland".
All four men agreed the UK economy needed to be rebalanced, with more emphasis on high-tech manufacturing and sustainable industries in addition to the City.
Mr Clarke said Labour had only recently discovered the virtues of manufacturing and that industry had "fallen as never before" during the past 13 years.
But Lord Mandelson said the contribution from manufacturing, in terms of volume and value, had not fallen and productivity in high-tech industries had risen sharply.
On foreign takeovers, Lord Mandelson said Labour would "raise the bar" to mean more shareholder support would be needed to allow controversial deals such as Kraft's recent acquisition of Cadbury.
But Mr Clarke said blocking foreign takeovers would be a sign of a "declining economy in a state of panic".
BBC News
