The Labour MP Heidi Alexander has announced that she is stepping down from parliament to take up a role at City Hall as Sadiq Khan’s deputy mayor for transport.

Her departure will start a fierce battle for the Labour candidacy in her safe seat of Lewisham East, where she won a majority of 21,123 votes last year.

Ms Alexander, 43, first entered parliament in 2010 and served as shadow health secretary under Jeremy Corbyn before she quit during the cascade of frontbench resignations in 2016. In the aftermath she accused him of running a dysfunctional team and said she had “hated being part of something so inept, so unprofessional, so shoddy”. She has come under intense pressure from hard left activists in her southeast London…