Shadow Brexit secretary is first candidate to get more than 22 backers needed to make ballot

Keir Starmer’s Labour leadership campaign has received a boost after he won the backing of the UK’s biggest trade union, Unison, and became the first person to get more than the 22 MPs required to become a candidate.

The shadow Brexit secretary is all but certain to be one of the names put to a vote of the Labour membership, after Dave Prentis, the Unison general secretary, declared the union would be endorsing him.

In another statement soon afterwards, Prentis said his union would back Angela Rayner to be the deputy leader, cementing her status as the favourite to win that role.

“This is a pivotal time for Labour,” Prentis said. “We believe – if elected by the membership – Keir Starmer would be a leader to bring the party together and win back the trust of the thousands of voters who deserted Labour last month.

“Keir has a clear vision to get Labour back to the winning ways of the past. He is best placed to take on Boris Johnson, hold his government to account and ensure Labour can return to power and once more change working people’s lives for the better.”

On Rayner, Prentis said she had “a long association” with Unison as a member and a former union rep, adding: “Angie’s popularity across the party means she is the right person to handle the challenges of this job.”

Starmer is thought to have about 26 backers, including Ben Bradshaw, David Lammy, and Debbie Abrahams. Jo Stevens, the former shadow Welsh secretary, set out her reasons for backing him in a blog, saying she asked every voter at the election who had reservations about Jeremy Corbyn who the leader should be. “With the exception of one person, the answer every time was Keir Starmer,” she said.

Rebecca Long Bailey, who is backed by a number of Corbyn allies, has at least 12 supportive MPs, from the party chairman, Ian Lavery, to John McDonnell, who said she would be a “superb” choice. Diane Abbott, the shadow home secretary, declared her support for Long Bailey on Wednesday.

Long Bailey also appears to be gaining big support among the 2019 new intake, including Navendu Mishra, Kate Osborne, Kim Johnson, Apsana Begum and Paula Barker.

Jess Phillips, on the Corbyn-sceptic side of the party, also has at least 11 MPs. One of her supporters, Wes Streeting, said she was “the person who captures the public’s imagination”. Her campaign said it was “confident we have the nominations needed to make it through to the next stage of this important contest”.

Lisa Nandy, who impressed many undecided MPs at a hustings on Tuesday night with her diagnosis of what went wrong at the election, has seven declared supporters. She won the backing on Wednesday of Jon Ashworth, the shadow health secretary, who said Nandy was the “authentic leftwing voice” for the leadership.

“Lisa brings a distinctive pitch to this campaign because many of the problems we’ve been facing in our more traditional seats, she’s been warning about that for some time,” he said.

The other two candidates – Clive Lewis and Emily Thornberry – have only one public endorsement each so far from Rachael Maskell and Fabian Hamilton respectively, suggesting they may struggle to make the ballot paper.

Lewis, a pro-European on the left of the party, announced on Wednesday that he would seek to work with the Green party if elected leader on a two-year project “to build the ideas, movements and democratic structures that would enable a green new deal to be introduced”.

“I have long been committed to a more plural politics and this is a tangible way of delivering on that commitment,” he said. “We need a new politics of collaboration and openness as the building blocks of the political forces and practices necessary for progressives to take power nationally by 2024 at the latest.”

If candidates win enough support among MPs, they will then have to get the backing of three affiliates, including two trade unions, or about 33 constituency Labour parties. Starmer is thought likely to meet that threshold with the Unison backing as well as local party nominations, while Long Bailey is also expected to meet the test by gaining the support of Unite and possibly other unions, as well as local parties.

However, it looks potentially more challenging for the other candidates to meet the test. After clearing those hurdles, the remaining candidates will face a vote of the party’s 500,000 or so members, any registered supporters who sign up, members of affiliated societies and trade union members.