Barry Gardiner is preparing to run for Labour leader in a shock last-minute entry to the race, HuffPost UK can reveal.
The shadow international trade secretary, an ally of Jeremy Corbyn, is seeking support from MPs in a bid to get on the ballot.
It comes as left-wingers and Corbyn loyalists fear the campaign of Rebecca Long Bailey, their favoured candidate, has been floundering while shadow Brexit secretary Keir Starmer races ahead.
Unite boss Len McCluskey is believed to have approached Gardiner and a number of other shadow frontbench figures asking them to stand.
However, McCluskey has denied he is uneasy with Long Bailey’s campaign and tweeted that he hasn’t been approached by Gardiner to support him as leader.
HuffPost UK understands Gardiner, the MP for Brent North since 1997, will centre his pitch on loyalty and has begun searching for a campaign team.
A source close to Gardiner told HuffPost UK: “Barry recognises the challenges the party faces over the next five years and believes he has the broad base of support, experience and loyalty to the party to win the race and take the fight to the Tories.”
Hours after the HuffPost UK story was published, Gardiner told the Guardian: “I am considering running and will decide in the next 24 hours.”
The shadow minister has served in frontbench posts in both the Tony Blair and Gordon Brown administrations.
Starmer has a commanding lead, according to a YouGov released last week, and has cleared the 22-MP hurdle to get on the ballot.
Gardiner could struggle to win enough nominations, however, with candidates including Clive Lewis and Emily Thornberry fighting to stay in the contest.
There are 202 Labour MPs and nominations close in five days.
Rebecca Long Bailey is in second place with the support of seven MPs. Jess Phillips has the support of six MPs.
Lisa Nandy, who impressed backbenchers with her pitch at the first leadership hustings in front of MPs on Tuesday night, has the backing of two MPs.
Thornberry has received the backing of one MP. Clive Lewis has not received the vote of any MPs so far.
Under party rules, once the required 22 MPs have been secured, leadership contenders then need to win 5% of local party nominations or 5% of party affiliates such as trade unions or socialist societies.
The contest will end on April 2, with the winner announced two days later.