A string of socialists lined up to drag Keir Starmer further to the Left on Tuesday in the race to become Labour's deputy leader.
Six MPs threw their hat in the ring to replace Angela Rayner as nominations opened in the fast-tracked contest.
Education Secretary Bridget Phillipson - a long-time ally of the Prime Minister - took an early lead on Tuesday night having secured the backing of 44 MPs.
Supporters believe her working-class background and close ties to trade unions could win her support but she appeared to be dismissed by one rival as a nodding dog candidate.
Ms Phillipson will be challenged by sacked Cabinet colleague Lucy Powell, who previously apologised for dismissing public concern about grooming gangs as a 'dog whistle' issue.
The former Commons leader once served as chief of staff to Ed Miliband and helped mastermind his doomed 2015 election campaign.
Ex-frontbencher Dame Emily Thornberry, who now chairs the foreign affairs committee, also threw her hat into the ring - promising not to 'nod along' with Sir Keir on contentious issues.
The Islington South and Finsbury MP, who has often been branded a 'champagne socialist' and sent a now infamous mocking tweet about a house draped in England flags in 2014, announced her support for a wealth tax as she confirmed her candidacy on Tuesday.
Bell Ribeiro-Addy, a hard-Left candidate who has criticised Labour's 'austerity approach', took aim at the leadership contest's 'unfair' timetable as she became the first to officially declare.
She has previously called for the UK to pay reparations for slavery, is a proponent of wealth taxes and a leading member of the Campaign for Nuclear Disarmament.
Paula Barker, a little-known backbencher, also threw her hat in the ring on Tuesday saying she was worried about the 'lack of geographical and political diversity' at the top of Labour.
The Liverpool Wavertree MP was a key welfare rebel, and quit her shadow ministerial post to vote for an SNP motion demanding a Gaza ceasefire in 2023.
Housing Minister Alison McGovern, the MP for Birkenhead, was the only candidate on the Right of the party to have declared on Tuesday night.
A Blairite, she formerly chaired of Progress - a political organisation associated with the development of New Labour.
Nominations for the deputy leadership opened on Tuesday and candidates have until 5pm on Wednesday to secure the backing of 80 MPs in order to reach the next round of the contest.
The candidates will take part in a hustings today in a bid to win over support of their Labour MP colleagues.
But the truncated nomination period has led some to accuse the party leadership of orchestrating a 'stitch-up' in a bid to 'dodge serious discussion'.
With Ms Phillipson securing the backing of 44 MPs, Ms Powell was in second place on Tuesday night with 35.
Ms Ribeiro-Addy had eight, Dame Emily seven, Ms Barker three and Ms McGovern two. Campaigning backbencher Stella Creasy, MP for Walthamstow, has also been rumoured as a potential candidate.
The ballot for candidates who clear the nomination hurdles will open on October 8 and close at noon on October 23, with the result announced two days later.