Chancellor Rachel Reeves had an 'almighty row' with younger sister and fellow Labour minister Ellie to stop her voting to let Andy Burnham return to Westminster, sources claimed last night.

The confrontation – at Ellie's home during her son's birthday party – was so heated that Rachel eventually stormed out, The Mail on Sunday was told.

The 'sisters at war' claims emerged amid mounting pressure this weekend on Ellie Reeves and other members of Labour's ruling National Executive Committee (NEC) to drop their veto on the Manchester mayor standing for a Commons seat and returning to Westminster – to potentially challenge Sir Keir Starmer.

At Mr Burnham's previous attempt in January, Ellie – who is Solicitor General – joined Sir Keir in voting to block the self‑styled 'King of the North' and prevent him standing in the Gorton and Denton by-election.

However, sources told this newspaper that Ellie did so only after No 10 got wind that she was minded to vote to allow the Manchester mayor to be allowed to stand as an MP.

In a frantic response, Downing Street was said to have telephoned Rachel Reeves, who at 47 is two years older than Ellie, to lean on her younger sister and 'sort it out' – unaware that at that very moment, the Chancellor was at her sister's house for her son's birthday party. 

To add to the drama, the siblings were also apparently playing The Traitors board game – based on the hit reality TV show about lies, deceit and treachery.

Rachel's intervention sparked a blistering row with Ellie, who was said to be especially furious that No 10 didn't call her directly to persuade her to change her mind.

One source suggested the incident also 'touched a raw nerve' as Ellie thinks Rachel is seen as the 'favourite child' in the family.

After angry exchanges, the Chancellor is said to have stormed off and left in her ministerial car without her shoes. 

However, Labour sources last night denied she left her footwear behind.

Without the support of the NEC, Mr Burnham is barred from standing for a parliamentary seat. But last night there were suggestions that Ellie would use her vote to back Mr Burnham this time. 

And in the face of reports that Sir Keir will still try to block him, he is understood to be ready to resign as mayor to sidestep the party veto.

Sources on the ruling committee also suggested Mr Burnham could win the nomination if he managed to get the unions on side. 

They play a powerful decision-making role. Unite leader Sharon Graham yesterday issued an extraordinary call for Sir Keir to go, saying: 'It is change or die. Now or never.'

A Labour Party spokesman said: 'Rachel and Ellie speak all the time and this isn't a true or accurate reflection of a private family event.'