GORDON Brown sacked Joan Ryan as his envoy to Cyprus today after she added her voice to calls for him to face a leadership contest.
Ms Ryan, a Labour vice chairman, said today it was time for the the party's "direction and leadership" to be debated openly.
She was among a number of usually-loyal MPs urging the party to issue leadership nomination forms ahead of its annual conference, which starts in Manchester next weekend.
Mr Brown was rocked last night when those demands were led by a member of his own Government.
Siobhain McDonagh, who said she had never crossed the leadership in 11 years as an MP, was promptly replaced as an assistant whip when her involvement in the apparent plot became known.
A Downing Street spokesman confirmed today that Ms Ryan had been "relieved of her duties" as the Prime Minister's special representative to Cyprus.
Labour's general secretary Ray Collins has rejected the MPs' call for nomination papers to be issued to all members of the parliamentary party.
In a letter to the MPs requesting the papers, he said he would not depart from the convention adopted since Labour came to power in 1997.
He suggested that most MPs knew they could request the papers if they wanted them.
He wrote: "A leadership election when in Government can only be held if requested by a majority of party conference on a card vote.
"We can only hold such a card vote at conference as required under B2d.(ii) if we receive notification from at least 20% of members of the House of Commons detailing a nomination.
"As the party has followed this procedure for the last 11 years I am confident that most members of the Parliamentary Labour Party are fully aware of their special responsibilities under rule to trigger the process which has not required the issue of nominations forms.
"I have considered this matter carefully. I have reached the conclusion that I have a clear responsibility to ensure that the party follows the procedures adopted by all my predecessors in respect of leadership elections when in Government."
Ms Ryan, MP for Enfield North and a former Home Office minister, was made Mr Brown's Cyprus envoy when he entered Number 10 in June last year. Earlier this month she took part in negotiations alongside Europe minister Jim Murphy over reunifying the island.
However, Ms Ryan stepped up the pressure on Mr Brown today by saying that a leadership contest was essential to meet the needs of the country.
"I think we need to have a leadership election to trigger a deep and far-reaching debate and those people in our party who have something to offer and are capable of leadership need to put themselves forward," she said.
"We need a multiplicity of candidates. That's a healthy thing to do and that's part of the democracy of our party. It's happening anyway, as I say, but it's happening behind closed doors."
Her comments came as a string of senior Labour MPs – including former health secretary Patricia Hewitt – called Mr Brown's strategy into question and urged him to come up with a "convincing new narrative".
Six former ministers were among 12 MPs to complain in an article for Progress magazine that the Government had failed to show how it would get through the economic turmoil.
Labour officials claim that fewer than 10 MPs have requested nomination papers to be sent out, although reports suggest that the figure may be slightly higher.
More names are expected to emerge over the coming days as part of what appears to be a co-ordinated move to destabilise Mr Brown.
If nomination papers were to be sent out, the rebels believe at least 71 would nominate somebody other than Mr Brown – the 20% of Labour MPs needed to trigger an election.
But Tony Lloyd, the chairman of the Parliamentary Labour Party, said today he was not aware of any widespread support for the position of Ms Ryan and Ms McDonagh.
"What it does represent is a handful of people who are not joined by the overwhelming majority of Labour MPs," he said.
Mr Lloyd also stressed how difficult it would be to actually trigger a leadership election.
"A stalking horse it does not seem as if there is, and don't forget that it requires the threshold of 70 Labour MPs, and this handful of people who are coming out of the woodwork are not going to trigger a leadership contest," he said.
Schools Secretary Ed Balls, a senior ally of the Prime Minister, also claimed today there was "very little chance" of Mr Brown being ousted before the next general election.
Other MPs who have requested nomination papers include former ministers George Howarth and, reportedly, Janet Anderson, Kate Hoey and Frank Field.
Backbenchers Jim Dowd and Graham Stringer are also said to have issued the request.
The involvement of Ms McDonagh, a minister who has a relatively safe seat and is not known for speaking out of turn, sent tremors through the party last night.
Her intervention also brought to an end a short period of relative security Mr Brown had enjoyed after summer speculation over his leadership had quietened down over the last couple of weeks.
The resulting frenzy looks set to overshadow a fightback by Mr Brown at Labour's annual conference.
In the Progress article, the 12 MPs led by Ms Hewitt suggested that voters' faith in the Government's economic competence had been shaken by the recent turmoil.
The group said ministers had offered "no explanation" as to how they would navigate the economy through its present difficulties.
It also questioned the wisdom of Chancellor Alistair Darling's 2.7 billion tax U-turn earlier this year.
"Labour needs to provide a convincing new narrative if left-of-centre politics are to remain the driving force in Britain," they wrote.
"This has to be more than a series of policy initiatives. It has to set a new framework for post-credit crunch Britain."
They said the party's most urgent task was to "renew confidence in our economic competence".
They described recent policies as being "defensive" when the party needed to be "bold".
"Our most urgent task is to renew confidence in our economic competence so that people know that the country will come out of the current downturn with a resilient economy and a cohesive society," they went on.
While Labour was "rightly" rejecting Tory solutions to previous recessions, they said, Labour had "no explanation yet as to how we are going to steer the economy through the troubled waters ahead".
"Clamour is understandably growing for measures to help families under financial pressure from rising energy prices and heavy mortgage costs.
"But one-off taxes and payouts, no matter how justified in their own terms, do not amount to a strategy."
The MPs called for better explanations of what the Government was going to do about "the things that affect people day to day: inflation and interest rates, household bills and mortgages".
They said there was a "yawning chasm" to fill between the Scottish National Party's "failures" on the left of the political spectrum and Conservative and Liberal Democrat positions on the right.
"Failure to do so would be a hammer blow, not only to the future of progressive politics, but also to our Government," they concluded.