Justice secretary Jack Straw has said he remains "absolutely convinced" Gordon Brown should not be forced to stand down as prime minister.
Following newspaper reports suggesting allies were campaigning on his behalf, Straw issued a statement warning MPs it would be a "big mistake" to stage a coup.
"I am absolutely convinced that Gordon Brown is the right man to be leading the Labour Party," he said.
"I was convinced of that when I was his campaign manager last year and nothing that has happened since has changed that view.
"The result in Glasgow East was obviously disappointing but it would be a big mistake for the Labour Party to now turn in on itself and indulge in a summer of introspection.
"We must instead focus relentlessly on the issues which matter most to people, listen to their concerns and work hard to address them."
He went on: "Gordon Brown is the best leader to lead us through these tough times. He has done so before and he will do so again."
Several papers reported on Sunday that MP George Howarth, a friend of the justice secretary, had approached fellow MPs and asked them to add their names to a list of people who want Brown to quit.
The loss of last week's Glasgow East by-election, which saw the SNP take Labour's 25th safest seat, has led to intense speculation that Brown will be forced to stand down.
Howarth told the Sunday Times: "Everybody's got to think long and hard about a number of issues, including policy, the party's popularity and the leadership."
But he said: "Jack is not up to anything. If anyone thinks I am collecting names for him, they are mistaken."
28 July 2008