Ed Miliband was last night given two weeks to reassert his authority over Labour as explosive claims emerged, threatening a fresh Blairite-Brownite rift at the heart of his party.
The Labour leader was accused by a number of his own MPs of failing to show leadership over the Falkirk affair which led to the dramatic resignation of his general election co-ordinator, Tom Watson, last week.
One frontbench MP warned that Mr Miliband must reform the party's relationship with the trade union movement, particularly Unite, before the summer recess or risk a crisis in the run-up to the party conference in September.
As the vote-rigging affair threatened to become the most critical issue for Mr Miliband in his two and a half year leadership, it was claimed yesterday that the shadow Foreign Secretary, Douglas Alexander, a senior Blairite in the Shadow Cabinet, was the target of a campaign by Unite to deselect him as Labour's candidate at the 2015 election. Unite denied this.
In another development yesterday, the former mayor of London Ken Livingstone revealed that Mr Miliband had called him on Friday evening to insist that he was not about to break the link between Labour and the unions. However, it is understood that Mr Miliband is considering some reform. There are a number of options that the Labour leadership is being urged to consider, including allowing members of trade unions to opt in to membership of the Labour Party, rather than see a levy from their union fees automatically paid to the party.
While this would lead to a significant fall in the amount of money the party receives from unions, supporters of the plan said it would also send a clear message to voters that Mr Miliband was not "in the pay" of Unite, and would help him pressure David Cameron to put a limit on the amount rich donors can give to the Conservative Party.
In contrast to the trauma Mr Miliband is suffering, his brother David is holding a farewell party for MPs who supported him in the 2010 leadership contest in London on Tuesday. David Miliband is leaving the UK for a job at the New York-based charity International Rescue.
On Friday Labour referred allegations that Unite paid the subscriptions of members in Falkirk, in order to secure the selection of Karie Murphy, Mr Watson's office manager, to the police.
Len McCluskey, the left-wing leader of Unite, angrily denounced the move and accused Mr Miliband of seeking a "punch up" with the unions. But it emerged last night that Mr McCluskey has been pressing for more direct influence within individual constituencies for more than a year.
In an interview with The Guardian in March 2012, Mr McCluskey said the union would be willing to give up its powerful block vote at Labour Party conferences in exchange for a greater say at constituency level. He told the newspaper: "If we were successful in getting more of our activists involved in grassroots constituency Labour parties, then the argument about 50 per cent block votes would become less relevant. That's what I'm looking to do. I'm not looking to hold on to a block vote for the sake of it."
A source close to Mr Miliband said: "Ed will speak about the way he wants to lead the party in future but we are proud of the link with three million people."
But Labour MPs worry that for the next two years before polling day the Prime Minister will use PMQs to claim that the party is "the political wing of Unite". One frontbencher said last night: "He has got to find a fresh settlement with the trade union movement, especially Unite. The domination of Unite and the way it's being run is giving trade unions a bad name.
"We need as many trade union members to be individual members of the Labour Party as possible. He has two weeks to re-establish himself as leader of the Labour Party. We are not the party of Unite, we are not the political wing of Unite. We are a broad-church political organisation which aspires to lead from the centre-left of British politics.
There is unlikely to be a leadership challenge as there is no obvious candidate. Last night Mr Alexander declined to comment on claims that he was targeted for de-selection by Unite when his seat, Paisley and Renfrewshire South, was due to be merged with another, Jim Sheridan's seat of Paisley and Renfrewshire North, under the boundary review – which has since been shelved.
A Unite spokeswoman said there was no truth in allegations that Mr McCluskey or Unite officials were involved in any plan to unseat the shadow Foreign Secretary: "It is complete nonsense, utter rubbish."
The union also said it would not be launching an internal investigation. "There is nothing to investigate, there is nothing questionable at all," the spokeswoman said.
David Cameron will attempt to exploit Labour disarray this week by pressing ahead with coalition reforms on education and privatisation of the Royal Mail.
He will seize on Ed Miliband's discomfort, exacerbated by the vote on an EU referendum on Friday in which all Labour MPs abstained.
Tomorrow Michael Gove, the Education Secretary, will unveil a new "rigorous" national curriculum after months of drafting and controversy.
On Tuesday, the Home Secretary, Theresa May, will give the go-ahead for an opt-out from a range of EU justice and home affairs measures, while Wednesday will see the latest stage in privatisation of the Royal Mail.
Prescott quits in press protest
John Prescott last night explained why he has resigned from the Privy Council, the prestigious body that advises the Queen, over the Government's plans on press regulation.
Writing in the Sunday Mirror, the former deputy prime minister said the decision for a Privy Council committee chaired by Nick Clegg to examine the newspaper industry's alternative proposals to the Leveson Report, before looking at a Royal Charter put forward by Parliament, "borders on a conspiracy to delay press regulation".
Mr Prescott quit the post, given to ministers and senior parliamentarians, after 19 years. The committee is examining the newspaper industry's plans on Wednesday.
He wrote: "I believe this approach borders on a conspiracy to delay press regulation. Much worse, it will embroil the monarchy in a possible conflict with Parliament and political division between the parties.
"The Privy Council must put Parliament and Parliament's [Royal] Charter first.