The Opposition rounded on the junior Coalition party and its role in the Budget.
Labour leader Ed Miliband focused on the cut in the top rate of tax from 50p to 45p as he accused Nick Clegg of incompetence.
"Only the LibDems could be dumb enough to think George Osborne's Budget [would be] a Robin Hood Budget – Calamity Clegg strikes again," he said.
But the Coalition hit back, claiming Labour had brought in a top tax rate that drove business away and raised effectively little for the Treasury.
There also appeared to be confusion within the Labour ranks about its own policy.
Senior party figures giving TV interviews appeared to offer conflicting views about whether Labour would re-introduce the 50p rate if it was to win a general election tomorrow.
Earlier, Mr Miliband had accused the Coalition of having the "wrong priorities".
The Conservatives and the LibDems were taking from the "squeezed middle" to give tax breaks to the rich, he said.
Labour also accused the Coalition of having a vested interest in tax cuts for millionaires, as it has more than 20 among its ranks. The deputy speaker had to intervene twice after Mr Miliband provoked fury by asking the Conservative frontbench: "Hands up in the Cabinet if you are going to benefit from the income tax cut?"
Labour claimed 14,000 millionaires would get tax breaks of around £40,000 and said anyone earning £5 million would be £240,000 better off.
The cut was the "Government's very own bankers' bonus", the party said.
But Tories said the 50p rate had been a "Trojan horse" tax which raised no money.
Former leadership contender John Redwood suggested cutting the top rate could bring the Treasury more revenue by stimulating economic growth.
"Surely if you are getting more overall, then it is worthwhile. Even Labour would accept that if you put the rates too high, [the rich] go away."
Mr Clegg defended the Budget, insisting that the rich had lost out and pointing to the rise in the tax threshold.
"Who are the losers in the Budget? The millionaires who weren't paying their fair share," he said. "The winners are over 20 million basic rate taxpayers who will be £220 better off."
But Labour MPs said that when judged overall, the Budget would give to the rich and take from those who needed it most.
Ann McKechin, the Glasgow Labour MP, said the Budget would hit women and children unfairly. "What does it say about a country when it allows tax cuts for the richest but at the same time allows the lives of more of its children to be stunted?" she asked.
The SNP said the Chancellor had ignored Scotland's need.
Stewart Hosie, the party's Treasury spokesman, said the UK Government had its "priorities all wrong", adding: "George Osborne has prioritised a tax cut for the wealthiest, while penalising public sector workers with a regional pay plan and adding to the burden faced by Scottish households and businesses through soaring fuel prices."