Shadow chancellor George Osborne has accused the government of "scrabbling around in a panic" and stealing the Conservatives' ideas on tax.
Mr Osborne said it was the Tories who were committed to lower tax
He said Gordon Brown had had ten years to reform inheritance tax and rules for non-domiciles, but only acted the week after the Tories unveiled their plans.
"He talks about setting out his vision of the country, but he has to wait for us to tell him what it is," he said.
He said it was a "cynical stunt" from a "desperate and weak prime minister".
Mr Osborne referred to Mr Brown's announcement at the weekend that he would not be calling a November election - despite weeks of speculation.
Mr Brown has denied his decision was swayed by favourable opinion polls for the Conservatives, saying he wanted to have more time to set out his "vision".
But responding to Chancellor Alistair Darling's pre-Budget report and spending review, Mr Osborne said: "I don't know why he even bothered to turn up. He should have called that election and let us give the Budget. Instead we had a pre-election Budget without the election.
"We all know that this report was brought forward so it could be the starting gun for the campaign, before the prime minister took the pistol and fired it into his foot."
Among Mr Darling's announcements were several issues raised at the Conservative Party conference - including inheritance tax, aviation duty and the tax status of "non-domiciles".
'Burying bad news'
Mr Osborne said the Labour government had had a decade to address these issues, adding: "A week after we put forward our plans the prime minister and the chancellor scrabbled around in a panic thinking of something to say."
"This is not leadership, it is followership prime minister," he said.
He also accused Mr Darling of glossing over government borrowing forecasts and criticised the level of government borrowing after 15 years of sustained growth.
"The chancellor has admitted that borrowing is going up again. Total borrowing this year is now expected to be £4bn higher than forecast.
"And we all waited for the moment when he would rattle off the borrowing figures for the years afterwards - he entirely missed them out. Talk about burying bad news."