Just months before the country goes to the polls, two former cabinet ministers are calling for a secret ballot on British Prime Minister Gordon Brown's leadership.
Geoff Hoon and Australian-born Patricia Hewitt have written to Labour MPs calling for the leadership issue to be sorted out "once and for all".
"This could be done quickly and with minimum disruption to the work of MPs and the government," said the letter.
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"Whatever the outcome the whole of the party could then go forward, knowing that this matter had been sorted out once and for all."
The letter was circulated shortly before the first prime minister's questions of the year, and Brown was reportedly aware of the attack before the session started.
The move by ex-defence secretary Hoon and former health secretary Hewitt comes with Labour trailing the Conservatives in opinion polls just months before a general election, due in the first half of this year.
'Unprecedented' challenge
Hewitt stepped down from the cabinet in June 2007 when Brown took over from Tony Blair as prime minister and announced last June that she was leaving parliament at the next election.
BBC political editor Nick Robinson said an attempt to topple a leader so close to a general election was unprecedented in Britain.
"However, those who want to see Gordon Brown go might look to Australia where Bob Hawke was installed as leader of the Labor Party and faced an election 25 days later," Robinson wrote in his blog.
"He won that election by a landslide, ending over seven years of conservative rule.
"Critically, however, that coup made Hawke leader of the opposition and not prime minister."
Downing Street said Brown was "getting on with the job", while Parliamentary Labour Party chairman Tony Lloyd said the call for a ballot lacked support.
'Business as usual'
"Geoff Hoon has very little support and that's the real issue for the parliamentary party - what we want is Gordon Brown ignoring this," Lloyd told the BBC.
In a statement, a Labour Party spokesman said the plan was "unconstitutional, not wanted and not needed".
"There is no provision for a secret ballot of MPs within the Labour Party constitution or rules, nor is there any provision whatsoever for a leadership election to be open only to MPs," the statement said.
Business secretary Peter Mandelson, widely credited with saving Brown's leadership after an attempt to oust him last year, backed the prime minister.
A spokesman for Mandelson told Sky News: "No one should over-react to this initiative. It is not led by members of the government. No one has resigned from the government.
"The prime minister continues to have the support of his colleagues and we should carry on government business as usual."
