Labour leadership hopeful Lisa Nandy has said she would give claimants a bigger role in designing an “empowering” welfare system.
In a speech, the Wigan MP said the current system lacked “human empathy” and was too complicated for people to understand.
She said she would reverse cuts to the welfare system by ditching planned reductions in national insurance.
She has been backed by Jess Phillips, who quit the race on Wednesday.
Ms Phillips told reporters she would be giving her first preference vote to Ms Nandy, with shadow Brexit secretary Sir Keir Starmer her second choice.
She said another candidate, shadow business secretary Rebecca Long-Bailey, was not the right leader for Labour at the moment, but “there’s no reason to say she can’t change”.
So far, Sir Keir Starmer is the only contender in the race to secure a place on the ballot, after he won the backing of shopkeepers’ union USDAW.
Shadow foreign secretary Emily Thornberry is the fourth candidate in the race to replace outgoing leader Jeremy Corbyn.
Speaking earlier on BBC Radio 4’s Today programme, Ms Nandy said changes to the welfare system had been undermined by the “values which permeate the system”.
She added the welfare regime has tended to “see people as problems to be solved, not potential to be realised”, and said the Labour party should ditch a “paternalistic” attitude on the issue.
In its election manifesto, Labour had argued for the universal credit scheme to be scrapped and replaced with an alternative system that “treats people with dignity and respect”.
Ms Nandy added that she supported the “principle” of the scheme, but “no support at all” had been offered to those being rolled onto the new system.
“If you want to empower people, you have to put the support in,” she added.
With Sir Keir’s place on the ballot secured, the three other candidates are locked in a battle to join him by securing support from local parties and affiliated groups.
To make it to the final stage, candidates have to secure nominations from 5% of constituency Labour parties (CLPs), or three affiliate groups – two of which must be trade unions – representing at least 5% of affiliated members.
Sir Keir cleared this hurdle after being backed by Unison, the UK’s largest union, and a second union, Usdaw, as well as environmental campaign group Sera.
As well as securing the support of GMB, Ms Nandy had already received the backing of the National Union of Mineworkers (NUM).
Ms Long-Bailey has so far only received the backing of bakers’ union the BFAWU, but is tipped to get nominated by the Unite union later this week.
So far Ms Thornberry has not been backed by any affiliate group, and had only secured two out of the required 33 CLPs which would help her onto the ballot.
Mr Corbyn’s successor – and the successor to his deputy, Tom Watson – will be announced on 4 April.