Hundreds of members of the TV and film industry have signed an open letter saying it is “time to put an end to this culture that turns a blind eye to predators and harassers operating in plain sight” in the wake of allegations made about the actor and producer Noel Clarke.

Some 20 women, who knew Clarke in a professional capacity, have accused him of misconduct.

Clarke has said he “vehemently” denies allegations of sexual misconduct or criminal behaviour but will be seeking professional help and has apologised “deeply” for his actions.

The letter, written by freelance producer Meriel Beale, an officer for trade union Bectu, and signed by figures including former Channel 4 commissioner Kelly Webb-Lamb and broadcasters Dermot O’Leary and Joe Lycett, said: “After reading the Noel Clarke allegations, many of us within the TV and film industry started sharing our own stories of sexual harassment and sexual abuse.

“His case is not a one-off and, shockingly, is not an extreme example.

“It has happened to so many of us that it seems normal.

“It has happened to so many of us at the hands of men in positions of power within the industry – whether industry colleagues, presenters or actors.

“It has happened in plain sight.”

The letter called on men to point out bad behaviour and for more women to hold senior positions in the industry.

It added: “We don’t want to be seen as ‘killjoys’ and we don’t want to anger the men into violence. It is a constant, terrifying tightrope. We are exhausted and we are angry.

“All of this contributes to us being undervalued in TV. Many men won’t recognise or notice sexist micro-aggressions – the low-level hum of sexism – and many women will accept it as part of the culture. It has been normalised, but it is not normal.

“We need more women in senior positions in TV and film. We need them to be allies and to be empowered to make real change. We need older women and women with caring responsibilities so that this filters down throughout the industry.

“We need women to be taken seriously. We need men to call out bad behaviour.”

In a statement to the PA news agency last week, Clarke said: “I vehemently deny any sexual misconduct or criminal wrongdoing.

“Recent reports however have made it clear to me that some of my actions have affected people in ways I did not intend or realise.

“To those individuals, I am deeply sorry.

“I will be seeking professional help to educate myself and change for the better.”