BBC Worldwide, Channel 4 and ITV are to launch a video-on-demand service offering more than 10,000 hours of TV programming.
The project has a working title Kangaroo as first revealed by MediaGuardian in June. Its launch next year could be a watershed moment in the development of on-demand video media in the UK.
Kangaroo, which one source has described as "wanting to do for broadband what Freeview did for digital TV", will be a joint venture in which BBC Worldwide, ITV and Channel 4 have an equal share.
In a joint statement, the partners said Kangaroo "will work independently as an aggregator of both joint venture partners and third-party content".