It is the backing that every leadership contender dreads: the endorsement of Peter Mandelson.
The former UK ambassador to Washington is understood to have told friends that Wes Streeting – who resigned as Health Secretary last week with an explosive parting salvo at Sir Keir Starmer – was the only candidate 'with anything new to offer or the ability to connect with voters'.
Mr Streeting has been at pains to distance himself from Mandelson – his former political mentor on the Blairite wing of the party – since the peer was sacked as ambassador last year over his links to paedophile financier Jeffrey Epstein.
In February, Mandelson was arrested on suspicion of misconduct in public office – he has denied wrongdoing – prompting
Mr Streeting to release messages that he had exchanged with the peer in which he criticised Sir Keir's government.
Last night, Mandelson told The Mail on Sunday: 'I have not made and will not make – categorically – any comment on candidates or aspects of this contest, so you have been misinformed.'
His appointment as ambassador has cast a long shadow over Sir Keir's administration, with ongoing rows over who knew what – and when.
Sir Keir's handling of the Mandelson saga has been a key factor in his MPs' loss of confidence in his leadership.
Wes Streeting and Peter Mandelson campaigning in the leadership hopeful's Ilford North constituency
The links with Mandelson have been seized on by Mr Streeting's leadership rivals as 'tarnishing' his brand, despite his frantic back-pedalling.
The pair first met when Mr Streeting was president of the National Union of Students and Mandelson was Trade Secretary, with the two campaigning together in general elections after Mr Streeting entered Parliament as an MP.
After releasing the messages – which also showed him complimenting Mandelson on his media appearances and seeking advice on political engagements – Mr Streeting then deleted photographs of the peer from his social media accounts.
Downing Street has been accused of a cover-up after refusing to hand over Mandelson's vetting file as part of a tranche of papers demanded by Parliament. The move which was condemned by the intelligence and security committee (ISC), which is overseeing the publication of the Mandelson files.
The ISC said that it had made its final decisions on redactions to 337 documents connected to the Mandelson appointment on national security grounds.
But in a statement, it raised 'concerns' about wider redactions.
The committee said that it did not think the Commons motion demanding documents related to the appointment allowed redactions 'other than on grounds of prejudice to UK national security and international relations'.