For the time being both companies will continue to operate as separate organisations and brands, meaning there will be no change to the services or terms and conditions for either group's customers.
Under a previous agreement, NTL which recently merged with Telewest, has also entered into a licensing arrangement with Virgin Enterprises which allows the use of the Virgin brand across the cable group's business.
It is thought that the company will start marketing a single portfolio of services under the Virgin brand some time early in 2007, if not sooner.
Branson, founder of the Virgin Group, said: 'Today, we've created a unique organisation - a new, soon-to-be-branded Virgin company - which will offer the very finest in 'quadruple' - the best-value, most -exciting TV, broadband, mobile and phone services in Britain.'
He added: 'We're entering a pioneering time, where the worlds of media, entertainment and communications are coming together - and through our new company, our aim is to offer consumers the very best, most sought-after choice available. You ain't, as the saying goes, seen nothing yet-'
NTL's chief executive, Steve Burch, said: 'This is a transformational deal for ntl:Telewest and good news for UK consumers. Virgin Mobile has a justified reputation for being one of the country's most customer-focused companies. This combined with ntl:Telewest's portfolio of competitively-priced, cutting edge products, will create a formidable competitor in the UK's fast changing communications and entertainment industries.'
Virgin Mobile's shares have now been de-listed from the London Stock Exchange.