Christine Shawcroft, the Labour official at the centre of an anti-Semitism row, is to be replaced by Eddie Izzard on the party's ruling body after she stepped down.
Ms Shawcroft, who has already resigned as chairman of the disputes panel - had been under pressure to quit her post on the national executive committee (NEC) after it emerged she opposed the suspension of a council candidate accused of Holocaust denial.
In a statement, Ms Shawcroft, a close ally of Jeremy Corbyn, said: "It has been a privilege to serve on the Labour Party national executive committee for the last 19 years, and I was standing down in September in any event. I have, however, decided to resign with immediate effect....