The prime minister has been condemned by one of his own Downing Street insiders as stilted and lacking personality in a sign that bitter infighting is breaking out over Gordon Brown’s performance.

Senior figures have warned that escalating conflict between Brown’s loyal old guard and a newly appointed team of No 10 spin doctors could cripple attempts to relaunch the prime minister and reverse a double-digit Tory poll lead before the local elections in May.

Downing Street is now trying to hunt down the source of the comments on Brown’s character, which were made to PRWeek, a trade magazine for spin doctors.

This weekend some of the prime minister’s most senior lieutenants were making barbed attacks on each other.

Veteran Brownites claimed that recruits to No 10 hired by Stephen Carter, the new strategy chief, cared little for Labour and were engaged in “shameless self-promotion”.

The old guard suspect it was one of Carter’s proteges who was the source of the insulting remarks.

“There are some people who have recently arrived in No 10 who regard it as ‘just another gig’ to be done for a couple of years before getting out and going on to something better paid,” said one senior Brown ally. “There is no loyalty. Most are not even members of the Labour party.”

The row is the latest evidence of deepening gloom in Downing Street. Other signs include:

— an urgent revamp of Brown’s public speaking style decided on by Carter after he was warned that the prime minister’s voice was so monotonous he could turn “the lyrics of Agadoo into a funeral dirge”

— discontent voiced by civil servants about the prime minister’s use of obscene language

— accusations by Brownite MPs that former cabinet ministers close to Tony Blair have been waging a “vengeful and destructive campaign”

With opinion polls consistently showing David Cameron’s Conservatives more than 10 points ahead, Labour MPs are increasingly concerned that the May local elections could lead to a “meltdown” not only in the southeast but even in Labour’s heartland in the north.

The Tory candidate for London mayor, Boris Johnson, will formally launch his campaign tomorrow with growing warnings from the polls that Ken Livingstone, Labour’s candidate and the incumbent, faces defeat.

The article in PRWeek discussed the need to improve Brown’s speeches and quoted a “senior” source as saying: “It has been acknowledged that the government’s messages are too cluttered and that Gordon needs to show a bit more personality.”

It followed publication in the previous edition of an “organogram” of the new No 10 power structure showing Carter and his recruits in prominent positions.

The initial prime suspect as the source of both stories was Nick Stace, 36, who was hired by Carter as special adviser on strategic communications from the consumer organisation Which?

A previous edition of PRWeek carried a highly complimentary piece about Stace’s appointment, with a comment from him saying, “Gordon Brown doesn’t want ‘yes’ men around him.”

However, yesterday, speaking from the doorstep of his home in Clapham, south London, Stace said: “It definitely wasn’t me. I don’t want to be drawn into the media spotlight.

“This is a great government and my job is simply to get us from where we are now to the next election.” “Super-mayors” with powers over police, schools and hospitals are to be introduced throughout England under plans aimed at preventing the break-up of the United Kingdom.

Gordon Brown is concerned that English voters are growing resentful of Scotland because of the extra autonomy given by the Holyrood parliament.

Ministers believe that a new class of strong mayors would be an effective way to reinvigorate local democracy.

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