Gordon Brown's "sabotage" of the Turner report on pensions has left the government in disarray, the Tories say.
Mr Brown: Opposes pensions earnings link
The report, due to be published next week, is aimed at solving the UK's growing pension crisis.
Mr Brown is thought to be concerned about proposals to link pensions to earnings and raise the retirement age.
Tory leader Michael Howard said the chancellor was the "only man" blocking vital reforms and the row showed he was not fit to be prime minister.
Mr Howard told BBC Radio 4's Today programme: "What Gordon Brown has done is attempt to sabotage this report before it is even published.
"We are told Lord Turner is livid. I'm not surprised he is livid. This is no way of going about things.
"The government is in total disarray. This is their Commission - they set it up.
"We should allow Lord Turner to present his report and then debate his findings in a proper and constructive way and a way that will try to aim for consensus, but that is not Gordon Brown's way of doing things.
"You only have to look at the embarrassed gibberish which Mr Blair was forced to utter at his press conference with (German Chancellor) Angela Merkel yesterday (Thursday) to see what a mess the government's in."
Mr Howard said there was a "growing consensus" building up around proposals, promoted by the Conservatives in May's general election, to get rid of means-testing and restore the link between the basic state pension and average earnings.
"That is what Lord Turner and the government's own Pension Commission are going to recommend next week," he said.
"The only man out of step is Gordon Brown."
He was speaking after an opinion poll in the Daily Telegraph suggested Mr Brown was a more popular choice to be the next prime minister than either of the two Tory leadership contenders.
Mr Howard said of the chancellor: "As people recognise his shortcomings, the flaws in the way in which he goes about the business of government...I think they will realise he is not the best man to lead the country."
Mr Brown's concerns on the earnings link first surfaced in a letter leaked to the Financial Times, in which he questioned Lord Turner's figures and suggested his plans were unaffordable.
But Mr Brown's closest political ally Ed Balls stressed this did not mean the chancellor wanted the entire report shelved.
And in a speech on Thursday night, Mr Brown said he believed the Turner report would start a national debate on getting a consensus on pensions changes.
"The issue is not reform versus the status quo; there must be continuing reform," he said.
"The issue is how we achieve the right reforms, reforms which are sustainable fair and affordable."
The BBC's political editor Nick Robinson said Mr Brown was "furious" about being portrayed by the opposition as an enemy of reform, and believed there were "elements around Tony Blair" encouraging this view.
"As for the leak of that letter yesterday, the Brownites are pretty convinced that it was a Blair ally, not with the prime minister's knowledge or backing, but that letter was leaked for that reason, to damage Gordon Brown," he told BBC Radio 4's Today programme.