The latest broadside against the prime minister has led to renewed speculation that friends of the chancellor are engaged in a concerted campaign to unseat Tony Blair.

The latest issue of the New Statesman has portrayed the prime minister as a "psychopath" and "psychotic".

The magazine, owned by the former paymaster general and close ally of Gordon Brown, Geoffrey Robinson, makes the case for the chancellor to take over the premiership in 2005.

A Brown government would constantly ask how to reduce poverty and promote equality, it says.

It adds that the chancellor would be a bigger vote-winner than the prime minister because Mr Blair "has lost so much public trust over the Iraq war".

Another article is headlined "What is the point of Tony Blair?", while a third says: "The question of Tony Blair's sanity can no longer be avoided."

Former Cabinet minister Clare Short tells the magazine that Blair is a "media star" who "thinks in soundbites" and "uses his charm to get what he wants".

In another article Charlie Whelan, Brown's former spin doctor, calls on the prime minister to sack Alastair Campbell.

The attack came as the prime minister began an extended foreign trip taking in America and Asia.

But back home allies such as David Blunkett leapt to his defence.

The home secretary issued a coded warning to Brown's allies.

He said they must not to let new rifts damage the standing of the party.

"We know who our opponents are in front of us, we know they're tribal. We know that they have very powerful voices through the media," he told Channel 4 News.

"Those behind us need to learn that if you stab your friends in the back, it is not your friends who succeed, it's your opponents."

As a result of the row, Friday's newspapers renew speculation that the relationship between the most powerful men in the government is again in trouble.

Since the Cabinet agreed its position on the euro, reports suggested that the tensions had eased.

With Blair facing difficulties over his policy on foundation hospitals and university top-up fees - as well as the failure to discover any Iraqi weapons of mass destruction - the new broadside will strengthen the impression of serious splits at the top of the government.