Momentum founder Jon Lansman has dropped his bid for the vacant post of Labour’s general secretary.
On Twitter, he said he had “decided to step back from the race” to focus on his role on the party’s ruling National Executive Committee (NEC).
He said he had achieved his aim of sparking debate about the party’s governance and encouraging others to stand for general secretary.
The Labour leadership favours Unite official Jennie Formby for the role.
Mr Lansman is understood to have come under pressure from Jeremy Corbyn to pull out of the race.
His surprise entry into the contest to replace Iain McNicol as general secretary sparked concerns about a power struggle between Unite, which is Labour’s biggest financial backer, and Momentum, the campaign group set up to support Mr Corbyn’s leadership.
Mr Lansman has argued for a much greater say for Labour members in the running of the party, including whether the general secretary should be elected by the membership, rather than chosen by the NEC.
According the Observer, Ms Formby was the “frontrunner” for the post but her allies were attempting to calm concerns she would launch a “clear-out” of Labour staff deemed to be insufficiently supportive of the leader.
In his statement, Mr Lansman said his main aim had been to open the contest up to other contenders.
“Over the last few days, in spite of media reports to the contrary including misogynist attacks on Jennie Formby in today’s Observer, NEC members have begun a productive, comradely debate about the future of the party.
“Whether the general secretary should be elected and what a transformed, member-led Labour party would look like are big, urgent questions – and I’m heartened to see members across the country openly debating them.”
He said “a number of party members” had been in touch with him to say they were considering a bid for the general secretary role.
He said would give his “full support” to whoever took up the post.
But he called for an end to the era of centralised “command and control” in the Labour Party, in which the views of members were “too often ignored” and over-ruled at the party conference.