Shadow chancellor George Osborne branded the pre-budget measures a " desperate, cynical stunt from a desperate and weak Prime Minister".
Mr Osborne accused Gordon Brown and Chancellor Alistair Darling of " scrabbling around in a panic" after the Tories' inheritance tax proposals were announced last week.
But he warned the public would see through the ploy of trying to copy their plans, adding: "This is not leadership of this country. It's followership, Prime Minister.
"It's not strong, Prime Minister. It is weak."
Rising to Tory cheers and Labour jeers after Mr Darling delivered his statement, Mr Osborne told Mr Brown: "I don't know why you even bothered to turn up.
"You should have called that election and let us give the Budget.
"Instead we had a pre-election Budget without the election.
"We all know this report was brought forward so it could be the starting gun for the campaign - before you took the pistol and fired it into your foot."
He said for 10 years the Prime Minister had been "sucking" millions of families into the inheritance tax net and pulling first time buyers into stamp duty.
"Now a week after we put forward our plans the Prime Minister and the Chancellor scrabble around in a panic trying to think of something to say.
"He talks about setting out his vision of the country. But he has to wait for us to tell him what it is."
Mr Osborne warned: "The public will see today's measures as a desperate, cynical stunt from a desperate and weak Prime Minister.
"But the public can tell the difference between a Labour party that sees this all as a cynical calculating game, and a Conservative party that believes in lower taxes and aspiration."
Mr Osborne said it was the Tories that were winning the battle of ideas.
"This Prime Minister's name may appear on the cover of books about courage but it's never likely to appear in the index.
"These cynical stunts should not detract from the fact that today was the day when the economic chickens came home to roost.
"Growth is down, borrowing is up, the spending rate is down and overall taxes are likely to go up.
"What a mess after 10 years in office."
He said Mr Brown should have prepared the public finances for a slow down in the economy, but he did not.
Government borrowing was "out of control" and now expected to be £4 billion higher this year than forecast.
"The real tragedy is that the Government shouldn't have borrowed in a boom and now there is nothing left to prepare Britain for the rainy days that may lie ahead."
The savings ratio had fallen from 5.5% to 3.5% this year - the "lowest savings ratio on record".
He told Mr Darling: "You didn't tell us that the estimates for the growth in disposable income for millions of families have also fallen sharply from 2.5% to 1.5% this year.
"You should be blaming your predecessor, not copying him."
Mr Osborne added: "The question people are asking is simply where has all the money gone?"
Mr Osborne claimed the tax burden was set to reach a record high, adding: "This is a tax raising pre-Budget report."
In 2010-11 there would be a £1.4 billion rise in taxes due to the measures announced today, he said.
Mr Osborne continued: "This pre-Budget report should have prepared our country for the new economic revolution.
"Instead we got overspun claims, desperate stunts and fake figures from a Government that has given us fake photos, fake troop withdrawals, fake hospital openings.
"All led by a Prime Minister who is increasingly seen as a fake."
And in a direct challenge to the Chancellor, he added: "We know the Prime Minister can't give straight answers to straight questions, let's see if you can do any better.
"Let's see if you can begin to restore trust in this weak and cynical Government."
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