Labour's general secretary Iain McNicol has stepped down to "pursue new projects" on behalf of the party and the wider Labour movement, the party announced last night.
McNicol, who was in charge of employing staff, running campaigns and organising conferences, thanked his staff for their work during a "tumultuous seven years".
"I will continue to support Jeremy Corbyn’s leadership and will work closely with him and our whole parliamentary team to take Labour to victory at the next General Election," he said.
Corbyn thanked McNicol and said he was "confident Iain will continue to play a major role in politics and our party".
The officers of the Labour Party will now meet to decide the process for the election of a successor.
McNicol clashed with Corbyn and his allies throughout Corbyn's time as leader of the party, and he is expected to be replaced by someone from the Labour left.