The BBC’s plans to offer TV on demand have approved by the BBC Trust subject to certain conditions.

It’s expected that many BBC TV shows will be available for download by the end of the year, although the full approval of the plans will follow a two-month consultation period. If it goes ahead, viewers will be able to watch popular shows online or download them directly to their computers. Shows will remain playable for up to 30 days after being downloaded or a week after the first time they’re viewed.

The BBC’s new iPlayer, a free piece of software that was known as the Integrated Media Player during its test phase, is central to the new service. It will allow you to download programmes using peer-to-peer technology, while digital rights management technology will prevent you from emailing content to other computer users or sharing it via disc.

The catch-up service has received cautious approval from Ofcom. The UK regulator has predicted that traditional television viewing may drop by 20-30 percent over the next five years, being replaced by on-demand services, and therefore advises that the BBC should reflect likely changes in audience behaviours. It also said that the iPlayer could have a detrimental effect on commercial rivals and may impact DVD sales and rentals.

Yesterday the BBC Trust published its provisional conclusions on the planned service and opened a period of consultation. The Trust will make its final decision before 2 May after it has seen the response it gets from viewers.

Diane Coyle, BBC Trustee and Chair of the PVT (Public Value Test) Steering Group, said that the BBC Trust feels the new on-demand services are “likely to deliver significant public value, and should be allowed to proceed”. This will, however, be subject to certain conditions in order to “reduce the potential negative market impact”. One of the conditions imposed was that the BBC’s original plans for the catch-up episodes to be available for 13 weeks be scaled back to 30 days. The Trust has also asked that ways to introduce parental controls are considered as the service could lead to children viewing post-watershed shows.

The Trust is now inviting feedback from the public, the commercial sector and BBC management team on its provisional conclusions before coming to a final conclusion in May.