Labour MP Heidi Alexander to swap Commons for City Hall
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".
Ms Alexander said she was "really excited" at her appointment, adding: "I know just how important it is we ensure everyone has access to a high-quality and affordable public transport network, with safe cycling routes across the capital."
She has been an MP since 2010, and was shadow health secretary between 2015 and 2016, resigning from the front bench with an attack on Jeremy Corbyn's leadership.
She has been a prominent pro-EU voice on the opposition benches and is co-chair of Labour Campaign for the Single Market.
Earlier this year she accused Labour of failing to come with a "common and coherent" Brexit position.
She is the latest Labour MP to quit for a job outside the Commons.
Another former shadow health secretary, Andy Burnham, is now the mayor of Greater Manchester, Tristram Hunt became director of the Victoria and Albert Museum and Jamie Reed left for a job in the nuclear industry.
A date has yet to be set for the by-election in Lewisham East. The Conservatives were well adrift in second place last year, with 10,859 votes to Labour's 32,072. The Lib Dems a distant third.