Barry Gardiner has announced he will not run to be Labour leader less than 24 hours after HuffPost UK revealed he was weighing up a bid.
Earlier the shadow cabinet minister insisted he could win a general election as he confirmed he was considering a run.
But after phoning Labour colleagues on Thursday, the Brent North MP admitted he did not command enough support.
In a statement, he said: “I want to thank all my colleagues as well as the party activists and members of the public who encouraged me to stand for the Labour leadership.
“I am now clear that at this late stage I cannot secure sufficient nominations to proceed to the next round. I have therefore decided not to stand for the leadership at this time.
“I will continue to serve the party loyally under whichever of my colleagues has the honour of leading our party forward to win the next general election.”
On Thursday, three more candidates reached the number of nominations from MPs and MEPs required to pass through the first round of the contest.
Shadow business secretary Rebecca Long-Bailey, Lisa Nandy and Jess Phillips all secured the 22 backers required to continue in the competition.
They join shadow Brexit secretary Keir Starmer, who was the first this week to bank the required number of supporters.
The numbers, published by Labour, puts Long-Bailey – branded leader Jeremy Corbyn’s “continuity candidate” – into second place with 26 nominations, and Nandy and Phillips are joint third with 22.
Starmer stretched his lead over the course of 24 hours by securing 59 signatories – up from 41 on Wednesday.
Lagging behind are shadow foreign secretary Emily Thornberry, who has seven supporters, and shadow Treasury minister Clive Lewis with four.