Walking With Dinosaurs could be among the first programmes made available

The clips, of up to three minutes, will include natural history footage and be available on the BBC website.

The service is the first stage of the Creative Archive initiative announced by former director general Greg Dyke.

If the service proves popular after 18 months, it will be extended across all genres of BBC programmes.

Ashley Highfield, head of BBC new media and technology, announced the launch on Wednesday, saying: "This is the BBC taking an innovation risk, but a risk that will add to the creative capital of the UK as a whole.

"It's all part of the BBC providing public access to its sound, television and film archives in a way that appeals to the new generation of media consumers."

Online programming

The public will be able to download clips for non-commercial use, keep them forever, and manipulate and add to them.

They will be able to pass clips on to one another and, in future, post user-generated material back on to the BBC's website.

The first phase will concentrate on material that is fully owned by the BBC.

In future, the BBC hopes to talk to independents and other rights holders about clearing the rights to other clips.

Mr Highfield also said the BBC was committed to developing further public use of broadband technology - alongside the online archive - when it came to enjoying the BBC's current output.

Mr Highfield pointed to this summer's online coverage of the Glastonbury music festival and the Olympic Games in Athens.

Viewers will be able to choose from a wide selection of broadcasts from both events.

At the same time, they will also be able to play games, interact with other users and access facts and statistics.