Easy access to online porn is making teenage relationships more abusive, according to one of the leading law officials in the UK.

Keir Starmer, the Director of Public Prosecutions, said that the “exposure of young people to all sorts of material” was a serious cause for concern.

And he said that the easy access to internet pornography for children and “emerging research” about increasing violence in teenage relationships could be linked, the Daily Telegraph reports.

Teenage domestic violence cases are currently being review by the Crown Prosecution Services to see if any action needs to be taken.

Earlier this week a schoolboy rapist avoided a jail term because, the judge said, he had viewed internet pornography.

The 14 year-old was given a three-year community order with supervision for the assault on a four-year-old girl.

The judge in Cambridge justified the sentence on the grounds that the boy had been “sexualised by the corruption of pornography”, and blamed society for what happened. Asked about the case on BBC Radio Five yesterday, Mr Starmer declined to comment on the case or the sentence.

But he added: “I have been concerned about the exposure of young people to all sorts of material, and the emerging research tends to suggest that there is a lot of abuse within teenage relationships.”

He published figures that suggested children aged 13 to 15 were as likely to experience violence as youths aged over 16.

Earlier this month a 12-year-old boy who raped a girl aged nine after watching hard-core pornography on the internet was spared jail. The judge ordered him to be sent to a children’s panel where he can be kept under supervision after hearing that he was “emulating adults”.

Tim Loughton, the children’s minister, is consulting on whether parents should be able to opt out of having pornography accessible from their home computers.

Claire Perry MP, chairman of the all-party inquiry on online child protection said: “The current way that we try to stop children seeing this damaging material is broken … We need to change the way filters operate on computers and accept that we all have a role to play.”

Jon Brown, head of the NSPCC’s sexual abuse programme, said: “Some of the most vulnerable children and young people are now getting access to hard core pornography. We have serious concerns about children accessing this online as it gives them an unrealistic and sometimes dangerous view of sexual relations.”

A study last September by Bristol University and the NSPCC found that violence in teenage relationships was much more prevalent than previously thought, with those from disadvantaged backgrounds twice as likely to be abused by violent partners.

Interviews with 44 boys and 38 girls aged 13 to 18, who were not in mainstream education, found physical, emotional and sexual abuse was commonplace.

A spokesman for Mr Starmer later said he was making “a general remark – a vague reference to teenage domestic violence issue, which he spoke about last year” and that it was “not a comment on internet pornography”.

Last year Mr Starmer warned in a speech that the UK was “clearly at risk of a whole new generation of domestic violence” in teenage relationships.

Meanwhile, more than 100,000 people have signed a petition calling for more to be done to ensure that internet service providers (ISPs) block pornography.

SafetyNet’s petition urges “the Government to force Internet Service Providers to make accessing pornography an adult only opt-in service”.

The campaign was started earlier this year, in a bid to protect children’s innocence online, by Premier Christian Media and Safermedia.

Peter Kerridge, CEO of Premier Christian Media, said: “It’s phenomenal how quickly the Safetynet campaign has gained the support of over 100,927 members of the public; and this number continues to increase daily.”

He added: “The public has clearly spoken out in support of this issue and it is our hope that the Government will now listen, and introduce legislation which will force ISPs to turn the porn default setting to ‘off’ and protect our children from adult content.”