Dame Louise Ellman has confirmed she will not be stand for re-election in the upcoming general election.
The Liverpool Riverside MP quit Labour earlier this month, citing the "growth of anti-Semitism" in the party.
Dame Louise, who has been an MP since 1997, said in her resignation letter that the party's leader Jeremy Corbyn was "not fit" to become prime minister.
At the time of her resignation, Labour said it was taking "robust action" to root out anti-Semitism.
More than 50 MPs have now said they will be standing down ahead of the 12 December poll.