Barry Gardiner has confirmed he will not be running for leader after four of his colleagues secured enough nominations to formally run for the top job.
Sir Keir Starmer had already got over the line, and now so has Rebecca Long-Bailey, Jess Phillips and Lisa Nandy.
Emily Thornberry and Clive Lewis trail, with seven and four nominations each.
A few hours after it was confirmed, Mr Gardiner, who had been weighing up his position, released a statement confirming he would not run.
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."
MPs running in the leadership campaign can be nominated by fellow MPs and by MEPs. They need 22 to secure a place on the ballot paper.
Mr Lewis has nominated himself, as have Ms Nandy, Ms Phillips and Ms Long-Bailey.
Angela Rayner remains the only deputy leadership candidate to pass the threshold, but Ian Murray is close, having secured 20.
The proposed candidates have until 13 January to secure the nominations they need to run and those with enough may well continue to add names to the list to beef up support.
The final count will be announced at 5.30pm on Monday.
Ms Long-Bailey has 26 nominations, and Ms Nandy and Ms Phillips both have 22.
Earlier, Ms Thornberry said she would give Jeremy Corbyn a 10/10 for "firing up the party", but a zero for his election performance.
Her stark rating was in contrast to Corbyn ally Ms Long-Bailey who raised eyebrows when she rated the outgoing leader 10/10.
News of Mr Gardiner's potential bid emerged on Wednesday night, and he confirmed he has been thinking about it, even though he is currently in Abu Dhabi.
He and Unite the Union general secretary Len McCluskey were forced to deny they had been discussing his bid, with Mr McCluskey refuted news he had asked Mr Gardiner to stand.
The winner of the leadership and deputy leadership contest will be announced on 4 April at a special conference.