Cameron Stout won the last series of Big Brother

Chief executive Mark Thompson called series four, won by fish trader Cameron Stout, disappointing compared with previous seasons.

He said that although no plans were in place for the next series viewers can be assured it will be "different".

Mr Thompson added there would a "fresh start" for the show in 2004.

"Although there was a lot to like in Big Brother 4, it just didn't grab my attention as much as Big Brother 2 or 3," he said.

"There may be some lessons to learn from that.

"It had some great and larger-than-life characters, but the overall magic between the housemates wasn't as strong as in previous years."

A little bit in the past sometimes Channel 4 has been guilty of slightly cynical choices Mark Thompson

Experiment

Mr Thompson also confirmed outgoing breakfast show Rise would not be replaced by another similar show.

Instead, Channel 4 is to experiment with a mix of programmes, with reality show The Salon and repeats of Friends - already a staple of the network's schedules - suggested as replacements.

Rise, which comes to and end on 19 December, has struggled in the ratings since it was launched in April 2002 despite a number of line-up changes.

Speaking at the launch of Channel 4's winter schedule, Mr Thomspon also admitted the channel had been too reliant on sex to boost ratings.

But he said sexual content had been reduced by half in the past year.

"I certainly think what we need to do is have a broad range of programmes late night on Channel 4," he said.

"A little bit in the past sometimes Channel 4 has been guilty of slightly cynical choices, like buying Temptation Island from Sky. That's not what Channel 4 was put on earth to do."

Cameron with his family after leaving the Big Brother house

Channel 4 is aiming to deliver more quality dramas, with a focus on depicting real life events including the Omagh bombing and the 11 September attacks.

Clocking Off writer Paul Abbott has been commissioned to write a drama called Shameless. based on his own childhood experiences.

Innovation

There will also be a medical drama, No Angels, about the lives of four nurses living in Leeds, which will fill the gap left by Brookside.

"Brookside has been one of the channel's greatest programmes but its demise offers us a chance for a fresh start in drama," said Mr Thompson.

"Channel 4's had brilliant one-offs and mini-series over the years, but our reputation for innovation in drama has never consistently matched that in entertainment and factual.