On a visit to a rape crisis centre in Ealing, west London, the Deputy Prime Minister spoke to a group of 16, 17 and 18-year-old girls about the issues raised in a new Government-funded TV advert, which aims to challenge the myths around sexual attacks.

Mr Clegg said the campaign had a strong message for teenage boys.

"What this ad campaign is seeking to achieve is to send an incredibly strong message to teenagers, and particularly to teenage boys, that, if you have sex with a girl who doesn't want to and doesn't consent, you're committing rape - it's a crime.

"When a girl says 'no', no means no, means no. There's no ifs and buts."

With NSPCC research finding that 33 per cent of teenage girls and 16 per cent of boys saying that they have experienced some form of sexual violence from a boyfriend or girlfriend, the campaign aims to help teenagers to recognise unacceptable behaviour.

• New rape campaign advert aimed at teenagers

  05 Mar 2012

"We've got such a highly sexualised culture at the moment and there are huge pressures.

"Any parent of a teenage girl will tell you there's huge pressures on teenage girls to conform to behave in a particular way, and I just think it's really important we give them the protection they need that when they say 'no' it means 'no' and the law is on their side," Mr Clegg said.

"It's not normal, frankly, for governments to do things like this or for politicians to talk about it. But I think the scale of the problem now is big, and it's a really big problem for a lot of teenagers and we need to address it."

The adverts are aimed at 13 to 18-year-olds and feature a teenage girl being coerced into sex by a boy as a party goes on downstairs.

The girl says "I don't want to", but the boy persists. A double of the boy then appears, watching the scene from behind an invisible wall.

The viewer is asked "If you could see yourself, would you see rape?"

The adverts will run for a month on youth TV channels, starting tonight, during programmes such as E4's Skins.