Labour MP Heidi Alexander is quitting Parliament to work for London Mayor Sadiq Khan.
The Lewisham East MP will become the new deputy mayor for transport.
It means there will be a by-election in her South London seat, where Labour won by more than 20,000 votes in last year’s general election.
Announcing the appointment, Mr Khan said Ms Alexander – who replaces retiring Val Shawcross – was “respected across the political divide”.
Labour MP Heidi Alexander to swap Commons for City Hall}