Ministers have previously said they are considering scrapping the two-child limit, introduced in 2017, as part of a delayed strategy on tackling child poverty expected to be unveiled this autumn.
Sir Keir Starmer has previously spoken of his desire to ditch the cap when economic conditions allow, without specifying exact circumstances.
Neither Powell nor Phillipson has explicitly called for it to be scrapped at the Budget in late November, but they have both been keen to stress they see the move as key to the party’s wider promises on child poverty.
Speaking to the BBC on Thursday, Phillipson said tackling poverty “brought me into politics” and she would fight on the issue “day, in, day out” if she won the deputy leadership contest.
“I am clear that everything is on the table, and that includes removing the two-child limit,” she added.
In an interview with the Guardian, external, she described the policy as “spiteful,” adding it had “punished and pushed children into hardship”.
Earlier this week, rival Powell called for Labour to be clearer about how and when it intends to scrap the policy, which she branded the “single biggest policy we could do to address child poverty”.
She also criticised “unforced errors” by the government over its botched attempt to cut disability benefits, which has been put on ice pending a review, and cuts to winter fuel payments that were partially reversed.