The chancellor said the government would get through its problems
Chancellor Alistair Darling has said the government needs to "sharpen ourselves up" and deliver a "clear message of what we are about".
But he told the Bloomberg news agency that the UK would "get through" the economic crisis because it was in a "fundamentally strong" position.
Mr Darling is the most senior minister to acknowledge concerns about the government's performance.
The Tories called the comments an "unprecedented attack" on Gordon Brown.
Asked about the economic global credit crisis, Mr Darling told Bloomberg: "We will get through this because the economy is fundamentally strong...
"But we have also got to make sure that in other areas we sharpen ourselves up, that we have a clear message of what we are about.''
His comments, made during a visit to China, come ahead of local elections in England and Wales on 1 May.
Shadow chancellor George Osborne, for the Conservatives, described Mr Darling's comments "as an unprecedented attack on the prime minister by his most senior cabinet colleague".
He added: "Even Gordon Brown never criticised Tony Blair in public.
"What started as anonymous briefings from backbenchers has now burst into the open with a public attack on Gordon Brown from the second most important person in the government."
Health Secretary Alan Johnson has defended the prime minister in a web chat on social networking site Mumsnet, describing him as "a serious man for serious times".
He added: "If you want somebody who will invite the cameras in while he shakes out the Shreddies over breakfast he's not your man, and he won't be telling how many girls he kissed behind the bike shed.
"That's not to say that Gordon's not good company - he's just a very private man and he is absolutely focused on the major problems which this country faces.
"I suppose you wouldn't expect me to say anything other than this, but I really do believe that he's a good man, leading a good government that's doing good things."