The Apprentice star was called in to oversee YouView’s route to market after it missed a number of expected launch dates.
His involvement helped the platform, which is jointly owned by the BBC, ITV, Channel 4, Channel 5, Arqiva, BT and TalkTalk, attract high levels of media and consumer attention.
Sugar regularly promotes YouView to his 2.7million Twitter followers.
Announcing his departure, the Peer, TV star and businessman said, “When I joined YouView in 2011, my brief from the shareholders was to use my experience in the electronics industry to get the product to market and into the homes of consumers.
“Having done that successfully, my job is complete and I will now focus my time and attention into my other businesses.
“I’d like to thank all those who are part of the YouView project, including its suppliers, staff and shareholders and I wish them every success for the future.”
A spokesperson for YouView said a new chairman will be announced “in due course.”