Conservative leader David Cameron said Gordon Brown looked like "a phoney" as they went head-to-head in their first Commons battle since July.
The clash came with the PM facing claims he "bottled" a snap election and stole Tory policy ideas on tax.
Mr Cameron said the PM was treating people "like fools" by denying opinion polls led him to reject a snap poll.
But Mr Brown pointed to the Tory grammar school row and said he would take "no lectures" from Mr Cameron.
Since his weekend decision not to hold a general election Mr Brown has sought to regain the political initiative with statements on Iraq and on his government's tax and longer-term spending plans.
But those tax plans - on inheritance tax, "non-doms" and green taxes on flights - have prompted accusations from both the Conservatives and Liberal Democrats that their policies have been stolen.
In the Commons, Mr Brown faced a volley of abuse from Mr Cameron, who accused him of lacking courage and "bottle".
'Flunk an election'
The Tory leader mocked the prime minister for denying that he would not have called an election even if the polls showed he would have secured a 100 seat majority.
"Do you expect anyone to believe that?" asked Mr Cameron, who added that Mr Brown's failure to hold a referendum on the EU treaty also "damages your credibility".
KEY POINTS: PRE-BUDGET
Growth forecast cut by 0.5%
Tax receipts down by £1.8bn, public sector net borrowing up by £4.3bn
Inheritance tax threshold raised to £600,000 for married people or those in civil partnerships
Crackdown pledged on "non-domicile" tax payers
10% tax rate on private equity capital gains abolished so private equity bosses pay more
Green taxes on flights not passengers from 2009
"You are the first prime minister in history to flunk an election because you thought you could win it."
He made fun of Mr Brown's book entitled Courage, saying: "Do you realise what a phoney you now look? Have you found a single person who believes your excuses for cancelling the election?"
He pressed the prime minister to say if the draft pre-Budget report that was written before the Conservatives' conference had included plans to cut inheritance tax or on levying non domiciles.
Mr Brown responded that the government had raised the exemption on inheritance tax on 10 occasions since 1997.
He said the Tory leader would have to explain why the Conservatives' plans would only generate £650m rather than the £3.5bn that they claimed.
Mr Brown said he would not take lectures from a man who had been for grammar schools, VAT on air fares and museum charges and then went against them.
Mr Cameron said if the prime minister had questions about Tory plans he should "find a bit of courage, get a bit of bottle, get into his car, go down to Buckingham Palace and call that election".
He added: "For 10 years you have plotted and schemed to have this job, and for what? No conviction, just calculation. No vision, just a vacuum.
"How long are we going to have to wait before the past makes way for the future?"
Mr Brown countered that Mr Cameron had said he was "a man who wanted an end to the Punch and Judy show" and "name calling".
"We are the government that has created 10 years of economic stability in this country. We are the government that adopted a minimum wage against Conservative advice."
Mr Brown said Labour had made the Bank of England independent and delivered record rises in investment in health and education.
Labour 'not blameless'
"We will continue to govern in the interests of the whole country," he said.
Health Secretary Alan Johnson acknowledged later that "it's not been the best of weeks" for Mr Brown.
He told the BBC he did not blame the media for the election fever that ended on Saturday, adding: "I'm not saying we are blameless ...If he [Mr Brown] had thought it through and decided a weekend earlier, we wouldn't be having all of this."
But he accused Mr Cameron of being a "PR expert", whose party had been "personal and insulting" towards the prime minister.
Earlier Liberal Democrat treasury spokesman, Vincent Cable, told BBC News 24 that Labour had actually stolen their ideas, rather than Conservative ideas.
He said: "Most of these policies were set out by the Liberal Democrats. We had set out this policy on changing the basis of aviation tax, the Tories pinched it from us and now the government have pinched it from them.
"I mean for the Tories to be bellyaching about it, it's like a gang of thieves complaining about their houses being burgled."