Team Sky sports director Steven de Jongh has quit his post after admitting to taking a banned substance earlier in his career.
Following the Lance Armstrong scandal, Team Sky had asked each member to reveal whether they had any past involvement with drugs - something which De Jongh admitted.
A Team Sky statement read: "Steven de Jongh has left Team Sky following three seasons as sports director. After the team reaffirmed its position on anti-doping, Steven disclosed that he had taken a banned substance earlier in his career as a professional rider."
Meanwhile, team head Dave Brailsford stated: "Steven deserves our respect for the courage he's shown in being honest about the past and it's right that we do our best to support him.
"There's no doubt about Steven's work with us or his approach. He's been a highly valued sports director and colleague over three seasons."
Disgraced cyclist Armstrong was banned for life and stripped of all his results from 1998 following doping allegations.
