I'm not proud of Big Brother, says C4 boss Lord Puttnam

Lord Puttnam hinted that the programme's days were numbered but admitted it would be difficult to replace such a money-spinner.

Big Brother, he revealed, accounts for 15 per cent of the channel's total revenue.

Lord Puttnam said the station needed a new remit to make sure programme makers, currently obsessed with controversy, were also "responsible and respected".

His comments, at the Hay-on-Wye literary festival, show how the fallout from the racist bullying scandal on Celebrity Big Brother earlier this year has jeopardised the channel's entire brand.

"I am not proud of the Big Brother row – I am not even proud of Big Brother," Lord Puttnam said.

"But Big Brother accounts for 15 per cent of the total revenue that keeps Channel 4 afloat.

"You have got to go some to replace that – but we will do it at some point, of course we will."

He added: "We're now dealing with programme-makers of a different generation. The way they see themselves regarded by their peer group is in terms of how controversial they could be."

There are signs that viewers are tiring of the predictably raunchy antics on Big Brother after ratings for Wednesday's first programme of the new series were down by a fifth on last year's opening show.

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Thursday's second episode drew 1.6million fewer viewers than last year.

The new series, which started with all-female housemates, also shed 2.3million viewers between Wednesday and Thursday.

On Friday night a 26-year-old former boyband singer, who describes himself as a "ladies man", was sent in to heighten the tension among the "ladettes" in the house.

Lord Puttnam, an Oscar-winning film producer, said time had eroded Channel 4's "sense of purpose".

"We shall renew that sense of commitment and that sense of purpose and get that "DNA" back in another context," he said.

The Big Brother race fiasco had made it harder, he added, to defend the broadcaster against some politicians' claims that it should be privatised, an option the Treasury is said to be considering.

Lord Puttnam confessed: "It doesn't help the political argument against privatisation."

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The media regulator Ofcom last week found Channel 4 guilty of "serious editorial misjudgment" over the way it handled the Big Brother racist bullying row in January in which the Bollywood actress Shilpa Shetty was subjected to racist taunts led by Jade Goody.

Three separate on-air apologies have been broadcast.

But Big Brother was not Lord Puttnam's only target.

He also criticised a recent Channel 4 show which questioned the scientific basis for claims that global warming was caused by mankind, branding it a "juvenile thing".

The Labour peer, who chairs the climate change committee in Parliament, said The Great Global Warming Swindle was the kind of show that goes out when "you take your eye off the ball".

This is not the first time he has cast such a critical gaze over Channel 4. Writing in the Royal Television Society's magazine Television he said Channel 4 was "effectively throwing the baby out with the bathwater" if it tried to be "challenging and controversial" without being "respected and trusted".

Lord Puttnam, however, defended the controversial Channel 4 documentary which will show pictures of Princess Diana immediately after the Paris car crash in which she died ten years ago.

He said: "It is actually a remarkably good documentary. I would be very proud to have my own name on it, very proud indeed."