Hammersmith and Fulham MP Iain Coleman is standing down because of ill-health, it has been announced.
Mr Coleman entered Parliament in 1997
The Labour MP, aged 47, first entered Parliament in 1997 and illness means he will not wait until the next election before leaving his job.
There is unlikely to be a by-election - but Labour's ruling council will now try to start the process of finding a new candidate for the seat.
Mr Coleman is a former mayor and leader of Hammersmith and Fulham council.
Mr Coleman, who comes from a political family, supported the Treasury's stance in its battle over Tube funding.
He was elected to the Hammersmith and Fulham seat as one of Labour's unexpected winners of the 1997 election.
Mr Coleman became a member of the Deregulation Select Committee in one of his earliest roles in Parliament.