She is running for the post against former Commons leader Lucy Powell.
Education Secretary Bridget Phillipson has said she wants to “unite” the Labour Party and beat Reform UK as she vies to become deputy leader.
She is running against Lucy Powell, who lost her post as Commons leader in the Cabinet reshuffle after Angela Rayner resigned as deputy party leader over her tax affairs.
Ms Phillipson promised to give party members a “strong voice” at the Cabinet table if picked.
“My message to Labour members is simple: I want to unite our party to deliver change so we can beat Reform at the next election and get a second Labour term,” she wrote in The Mirror as she prepares to launch her campaign with a rally on Sunday.
She vowed to keep up Ms Rayner’s “campaigning role” as deputy leader, saying the party cannot afford to “reopen old wounds” and become divided again.
She said: “The path to victory runs through all of our regions and nations, towns and cities, countryside and coastlines.
“But we won’t if we’re not united. Divided parties don’t win elections. We cannot afford to hand Nigel Farage and Reform a crucial advantage with elections in Scotland, Wales and local elections right around the corner.”
The Education Secretary and the recently sacked Commons leader were the only candidates to secure enough support from fellow MPs to make it past the first round of nominations.
They now need to secure the support of 5% of constituency parties or at least three affiliates, including at least two affiliated trade unions.
The ballot for candidates who clear the nomination hurdles will open on October 8 and close at noon on October 23, with the winner announced on October 25.
The contest is seen by some as a referendum on the Prime Minister’s leadership, which has come under pressure amid the loss of two of his Government’s household names – Ms Rayner and Lord Mandelson – within a week.
Ms Powell has called for a “change of culture” at Downing Street to make it better connected to MPs.
“We’ve got a bit of a groupthink happening at the top, that culture of not being receptive to interrogation, not being receptive to differing views,” she told The Guardian.
It comes amid frustration in the party’s backbenches.
MP Clive Lewis publicly questioned Sir Keir Starmer’s leadership, telling the BBC the Prime Minister does not seem “up to the job”.
Barry Gardiner meanwhile said “toxic” resentment was festering among the party’s MPs and rank and file members.
Shadow foreign secretary Dame Priti Patel added her voice to criticism of the Prime Minister, saying the handling of Lord Mandelson’s departure showed the UK was “unstable and unprofessional”.
Writing in the Sunday Express, she said the response to the issue and a failure to sack Ms Rayner showed Sir Keir was “a PM who is incapable of standing up to scrutiny”.
