The BBC plans to spend �266m over the next three years on flagship documentaries like Walking with Dinosaurs and Blue Planet.

Both series were massive hits and have changed the face of science and nature programming.

Also on the way is increased spending on "landmark drama" with �50m to be spent over the season 2002-2003.

We need to take more risks and add more complexity to the programming

Jana Bennett

Upcoming landmark documentaries include a history of Moses and The Ship, which will see volunteers re-enacting the voyages of Captain Cook on a replica ship.

It is understood that having had successes with series like The Human Body, the atmosphere is right for risk-taking with large budget documentaries and even current affairs.

In an interview with the Daily Telegraph Jana Bennett, the new BBC director of television, said current affairs were currently strong, particularly in the wake of the Panorama programmes on alleged security force complicity in the murder of Northern Ireland solicitor Pat Finucane.

She said: "BBC One has to be successful, because it needs to reach a broad audience.

Walking with Dinosaurs was a ratings success

"But when it is successful, it can also - and must - take risks."

Revealing plans for a new primetime documentary strand on BBC One, Bennett said: "The cornerstones of the channel are there with confident dramas such as Auf Wiedersehen Pet and Cutting It. Now we need to take more risks and add more complexity to the programming."

She also seemed to suggest channels would become more diverse, despite pundits' belief that television will become more specific with the advent of digital.

"BBC One needs to build back more layers into itself. It is not only an entertainment and drama channel but one with broad reach and a fantastic showcase."