By Darren Waters BBC News Online entertainment staff in Edinburgh

Humphrys, who presents the Today programme, told an audience of media executives at the Edinburgh Television Festival on Friday night that "some of our worst television is indeed indefensible".

Humphrys is known for his tough-talking style

He called for greater regulation of terrestrial television and even possible government intervention to ensure standards are maintained.

The three-day festival is host to the most important figures in British television, and features talks and seminars given by the heads of Channel 4, Five, Sky and the BBC.

Humphrys used the prestigious McTaggart lecture to say reality TV "eroded the distinction between the public and the private, which is a profoundly important aspect of our culture".

He called Channel 4's hit show Big Brother "damaging" and said the most recent show had "bequeathed us a legacy; the way to get ratings is to get evil".

Reality TV turns human beings into freaks for us to gawp at John Humphrys

People who wanted to watch reality television could do so on subscription channels but society should "limit the harm" by stronger regulation of commercial channels by the government, he said.

The Cardiff-born presenter said TV was now "a battle between people who are concerned about society and those whose overwhelming interest is simply to make programmes that make money".

Humphrys also warned that news coverage of politics should not be made "more fun" in an attempt to boost public interest.

The quality of the best television is not just as good as it ever was, I suspect... some of it is even better John Humphrys

He said he disagreed with the former BBC director general Greg Dyke who said it was the broadcaster's job to make politics less boring by making the coverage less boring.

"We shouldn't be trying to lure [viewers and listeners] into politics by pretending that it's just another game show.

"Greg got it wrong," he said.

And as the presenter on Radio 4 when Andrew Gilligan's news report into the government's Iraq dossier unleashed a storm of controversy, he said news needed "more, not less in-depth interviewing of politicians".

I've been reminded that television... can help maintain the momentum that takes us from barbarity to civilisation John Humphrys

In a thinly-veiled dig at the BBC's measures taken since the Hutton report criticised the BBC's approach to news, he said mistakes would always be made "however many notes we take and however many people we send back to college".

HAVE YOUR SAY Love them or hate them, reality TV programmes are here to stay Darren Coleman, Westbury, UK Send us your comments

He told the conference he has not watched television for the last five years, but said he had based his opinions on watching programmes sent to him by executives as examples of the best of the medium.

He praised programmes such as Channel 4's Operatunity and the BBC's Life of Mammals, saying he had been "informed, entertained and deeply moved by some of what I've seen".

Operatunity's winners were Denise Leigh and Jane Gilchrist [R]

"I've been reminded that television... can help maintain the momentum that takes us from barbarity to civilisation".

But he said a "vast amount of the rest is simply mediocre" and did not tell the audience if his recent viewing would mean he would become a regular viewer again.

The veteran broadcaster expressed incredulity that programmes such as Your Face or Mine, The Pilot Show, Banzai and Nip/Tuck were considered quality television.

Examples of good television "cannot pay the dues of the bad when the bad is indefensible", he added.

I'm personally profoundly relieved that the BBC has avoided the worst excesses of reality television John Humphrys

And television was "more aggressive and confrontational" and "vulgar and obsessed with sex" than he remembered.

He warned that such television could "coarsen" and "brutalise" and said the level of aggression he found in soaps "fits my definition of harmful - especially given that they're broadcast pre-watershed".

He also admitted that the BBC produced its share of rubbish and quality programmes - the corporation's responsibilities were greater than they have ever been, he added.