Harriet Harman has said that Conservative tax policies amount to a "millionaires' manifesto".
Answering questions from MPs on Wednesday, the Commons leader hit out at Tory plans to raise the inheritance tax threshold to £1m.
But for the Conservatives, William Hague sought to portray ministers as being at odds with the Bank of England in their efforts to boost the economy.
And Liberal Democrat Treasury spokesman Vince Cable suggested that Bank of England governor Mervyn King's opposition to any further stimulus measures amounted to "a very British coup d'etat".
Hague also renewed Conservative criticism of the government over the slow implementation of policies designed to help businesses and householders.
He told MPs that no loans have been guaranteed under the working capital scheme, adding that ministers are "behind the game".
"Isn't it time to get on with these things?" he asked.
Harman insisted, however, that £5bn is being released to businesses and that tax payment deferrals have helped 93,000 firms.
On King's comments to the Treasury select committee on Tuesday, Hague said it was "exceptional and extraordinary" for him to speak out ahead of the Budget.
Hague called on Harman to agree with King or leave the public to assume that the government "is now in open disagreement with the governor of the Bank of England".
The Commons leader, standing in for the prime minister who is visiting New York, agreed that it is "a defining time", saying that the government would take action on the recession while the Conservatives would "do nothing".
And she said the Tories would help "3,000 millionaires" with their proposed inheritance tax cut.
"We want to make sure that we give help to 22 million families with tax cuts," she said. "They set out their stall, it is the millionaires' manifesto".
Cable also focused on the Bank governor's remarks, suggesting King had taken control of fiscal policy.
He said it was "a very British coup d'etat" with King "putting the government under house arrest".
The Lib Dem frontbencher also called on the government to concentrate on "taxing and spending more efficiently and fairly", withdraw the VAT cut and focus on helping the low paid.
Harman responded that the VAT cut was "one of a range of measures", with the government also investing in housing and public transport.
Dods Parliamentary Communications Ltd