Virgin Media chief executive Steve Burch has stepped down with immediate effect after citing family reasons.
Chief operating officer Neil Berkett will assume the role of acting chief executive and a search for Mr Burch's replacement will begin shortly, the company said.
A spokeswoman for the group said Mr Burch, who joined the company in January 2006 when it was called NTL, was not sacked.
Mr Burch joined NTL in January 2006 and led it through the merger with Telewest, the acquisition of Virgin Mobile and the rebranding of the company under the name of Virgin Media.
Shares in the group, which trade on the New York stock market, opened down 1.3 per cent in early trade.
The group has lost customers recently over a high-profile pricing dispute with rival Bskyb, and earlier this month it was forced to postpone a sale of the company as it became clear that buyers would not have access to the debt needed to do a deal right away.