Keith Vaz
He was under investigation by The Parliamentary Commissioner for Standards.
Probe comes after Vaz was appointed to Parliament's Justice Committee.
Labour MP stepped down from home affairs committee after escort scandal.
She will have to defeat Labour colleagues to win the chairmanship
The scandal has already cost him his place on the Home Affairs Select Committee.
His resignation comes days after revelations about his private life
Labour MP under pressure over escort scandal
'What Keith does is for Keith'