By contrast, Phillipson, as a cabinet minister, would be expected to be more supportive of the government and its policies.
Announcing her decision to run, Phillipson described herself as a “proud working-class woman from the North East” who could bring “determination to every battle ahead of us”.
“Because make no mistake: We are in a fight. We all know the dangers Reform poses our country.
“But not only am I ready for it: I’ve proven we can do it. I’ve shown we can beat Farage in the North East, while staying true to the Labour Party’s values of equality, fairness and social justice.”
Asked about the contest on BBC Breakfast, Health Secretary Wes Streeting said he had not yet made up his mind about who he would support.
He added that deputy leadership contests usually took place after Labour had lost an election, but this one was taking “place in the context of a party who are in government, and whose focus has got to be delivering the change we promised at the last election”.
Whoever wins the contest, David Lammy will remain as deputy prime minister – a role which is appointed by the prime minister, rather than decided by Labour Party members.
Last week, Rayner resigned from the role, as well as her post as housing secretary, after admitting she failed to pay enough tax on her £800,000 flat in Hove.
Sir Laurie Magnus, the PM’s ethics adviser, found she did get legal advice when buying the property, but failed to seek further expert tax advice as recommended.
Rayner said she took “full responsibility for this error”, adding: “It was never my intention to do anything other than pay the right amount.”