Lisa Nandy is the second Labour leadership hopeful to get on to the final ballot, after Chinese for Labour announced it was supporting her.
The Wigan MP joins shadow Brexit secretary Sir Keir Starmer, having already got backing from the GMB union and the National Union of Mineworkers.
To progress, hopefuls need the support of three unions and affiliate groups representing 5% of the membership.
Emily Thornberry and Rebecca Long-Bailey are yet to reach the threshold.
Jess Phillips quit the race to replace Jeremy Corbyn on Tuesday. She has said she will be giving her first preference vote to Ms Nandy, with Sir Keir her second choice.
She added that shadow business secretary Mrs Long-Bailey was not the right leader for Labour at the moment, but "there's no reason to say she can't change."
Chairwoman of Chinese for Labour - a group affiliated to the party - and Luton North MP Sarah Owen said: "Only in power can Labour make the radical changes that are so desperately needed for our towns and communities.
"We believe that Lisa is the right candidate to take us there."
Chinese for Labour aims to promote the interests of British Chinese and East Asian people in the Labour Party.
Reacting to the endorsement, Ms Nandy said: "As someone of mixed heritage, I'm incredibly proud that it is Chinese for Labour who have secured my place on the ballot paper.
"They do incredibly important work to ensure we are a representative and inclusive party that can truly speak for modern Britain."
In a speech earlier, Ms Nandy said she would give claimants a bigger role in designing an "empowering" welfare system.
The current system lacked "human empathy" and was too complicated for people to understand, she said, and promised to reverse cuts by ditching planned reductions in national insurance.
She said the universal credit system, which rolls six benefit payments into one, was "fundamentally flawed" and could not recognise claimants' changing circumstances.
"That's why I say Labour has to scrap it and replace it with a system that is able to deal with the complexity and the lived reality of people in it."
She also said she backed higher taxes for bigger firms that fail to pay their staff the minimum wage, adding the government was often forced to "top up" low wages through the benefits system.
Mr Corbyn's successor - and the successor to his deputy, Tom Watson - will be announced on 4 April.
With Sir Keir's and Ms Nandy's places on the ballot secured, the two other candidates are locked in a battle to join them by securing support from local parties and affiliated groups.
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.
Mrs 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 has only secured two out of the required 33 CLPs which would help her onto the ballot.
In an interview with the BBC's Andrew Neil, the shadow foreign secretary said the "right way" to entice Labour voters back was to have "strong leadership" and to listen to people.
She said the party needed to be clear with its priorities, and for her, the number one priority was social care.
In the contest to find Labour's new deputy leader, only shadow education secretary Angela Rayner has received the required support so far.
She faces competition for the role from Scotland's only remaining Labour MP, Ian Murray, shadow equalities minister Dawn Butler, Tooting MP Rosena Allin-Khan and shadow justice secretary Richard Burgon.
Ms Rayner has been backed by the GMB union, NUM, Unison and Usdaw, while the BFAWU is supporting Mr Burgon and Chinese for Labour is backing Ms Butler.
Ms Phillips has endorsed Mr Murray, saying he has put forward "a positive vision not only for our party, but also for the country".
"He recognises that we can't just talk to ourselves - we must listen to voters in seats we held, seats we lost and seats we have never held," she said