Berkett started at in the chief operating officer role in 2005.
At the same time, Jacques Kerrest, the current chief financial officer, is to leave the company in early April. Kerrest joined NTL as it was in 2004 and an executive search for a permanent chief financial officer is now under way.
Jim Mooney, chairman of Virgin Media, said: "Neil has a long and successful track record of managing and developing consumer-facing businesses and the board is delighted that he has accepted the role of chief executive officer.
"As COO, he was the driving force behind the successful integration of NTL and Telewest. Since taking on the role of acting CEO six months ago, he's demonstrated that he has both the strategic vision and operational experience to take the company into its next phase of growth."