Channel 4 is to sell regional advertising packages on BSkyB from next week, making it the first terrestrial TV broadcaster to offer such a deal.
The move will put pressure on ITV, which is still locked in talks with Sky about access to its electronic programme guide, prompting advertiser concern about ITV's presence in multi-channel homes.
One of the obstacles ITV has cited is the cost of providing a regional service on Sky. ITV has 27 sub-regions to which it would want to broadcast.
Channel 4 will be able to offer regional advertising packages across London, the South and Northern regions, as well as the Midlands, Scotland and Ulster. Until now Channel 4 has only broadcast London advertising packages.
Granada Media's chief executive, Steve Morrison, pledged to Campaign earlier this year that ITV will be on Sky by the end of 2001. Responding to Channel 4's move, an ITV source said: 'ITV can and will be on Sky.'