ONdigital plans to spend £8m through incumbent agency BMP to promote new TV internet product ONnet, which will roll out from September 18.

The bulk of the spend will go on a pre-Christmas TV flurry designed to boost subscriber numbers, although press and poster advertisements will also be used. "We plan to make this one of the Christmas must-haves," said an ONdigital spokesman.

Some of the money has been earmarked to promote ONdigital's new sports channels and increase the number of subscribers to its TV service.

The ONnet boxes will allow for full internet access via the TV, only work in conjunction with an ONdigital box and carry a £5 monthly fee. Subscribers receive a free cordless keyboard, while a deal with BT offers users special internet call discounts of 2p per minute peak and 1p per minute off-peak.

ONdigital will integrate the internet service with the broadcast stream. It means viewers will be able to click straight to the internet from programmes and ads, although it has yet to be determined whether there will be sufficient demand for this type of service.

As with other TV internet products on or coming onto the market, ONdigital has not pre-bundled RealPlayer software with the boxes and says it has no plans to incorporate this application.

Given the number of websites (Big Brother, Jailbreak, and so on) broadcasting video content via RealVideo, this could be a shortsighted strategy. However, ONdigital is providing Flash, Shockwave and Javascript reading software, and will allow audio to be streamed.

Research company Verdict estimates that one-third of online shopping transactions (£4bn) will be through the TV by 2005.

BBC Resources has developed a portal that will push dozens of "preferred retailers" Ð in other words, those that have paid to be on the default home page Ð and it will pay ONdigital a small commission for each sale.

A prepaid package will bundle a basic ONdigital subscription and 12 months of ONnet for £159.