Ken Livingstone has said he is resigning from the Labour Party.
The ex-London mayor has been suspended since 2016 in a row over allegations of anti-Semitism following comments he made about Hitler and Zionism.
Mr Livingstone told the BBC he was quitting after his lawyers advised him if he lost his case and was expelled, it would take at least two years before any legal challenge was resolved.
Jeremy Corbyn said it was a sad moment but it was the “right thing to do”.
Mr Livingstone, an ally of party leader Jeremy Corbyn, has always maintained that comments he made about the Nazi leader supporting a Jewish homeland when he first came to power in the early 1930 were historically accurate.
Last week, shadow attorney general Shami Chakrabarti called for Mr Livingstone’s expulsion – signalling to some that the party leadership had now turned against him.
He was awaiting a fresh disciplinary process due to start this week.
Mr Livingstone was expelled from Labour in 2000 after challenging the party’s official candidate in the mayoral contest but returned to the fold later.
Ken Livingstone to quit Labour amid anti-Semitism row}