Labour has named David Evans as the party’s new general secretary, sources have told the BBC.
The National Executive Committee met on Tuesday to chose its most senior official after the resignation of Jennie Formby earlier this month.
Six candidates were shortlisted for the post, but Mr Evans was thought to be favoured by the leadership.
However, several unions were believed to have wanted someone from the left of the party.
One of the first tasks for Mr Evans – who worked for the party under Tony Blair – will be responding to the findings of an inquiry by the equalities watchdog into Labour’s handling of anti-Semitism cases within the party.
The Equalities and Human Rights Commission’s report is due to be published soon, with the party’s leader, Sir Keir Starmer, having already committed to accepting its recommendations and setting up an independent complaints process.
Ms Formby – who was a close ally of former leader Jeremy Corbyn – left the role after two years by “mutual consent” following Sir Keir’s election as leader in April.
The choice of successor is seen as a crucial step in the new leader’s attempts to unify the party after December’s heavy election defeat and years of factional in-fighting.
Allies of the new leader have a slim majority on the NEC after elections last month.
But the committee, which is made up of MPs and other elected officials, trade unionists and representatives of local parties, remains finely balanced, after years in which it was dominated by supporters of ex-leader Mr Corbyn.
Mr Evans was regarded as the frontrunner in the contest, with his backers including Morgan McSweeney – Sir Keir’s chief of staff.
As assistant general secretary of the party between 1999 and 2001, he played a leading role in Labour’s victory in the 2001 election.
But some union leaders said Mr Evans – who subsequently left to found a political research and consulting company – is a polarising figure who has historically sought to reduce the influence of the left.
The other candidates were Andrew Fisher, who worked as head of policy for Jeremy Corbyn, Karin Christiansen, a former general secretary of the Co-operative Party, Andrew Byron Taylor, the former head of the Labour group on Basildon Council, former MEP Neena Gill, and Amanda Martin, president of the National Education Union.