Three out of ten child sex crimes in Suffolk are committed by children or youths, according to police figures.

The 30% ratio has led to the NSPCC voicing fears that the internet and social media are warping young minds by blurring the lines between right and wrong.

Suffolk Constabulary figures show 242 child sex offences in the past two years were allegedly carried out by offenders under the age of 18.

Separate police figures show that in 2011/12 and 2012/13 there were 808 children in the county who reported they had been abused.

Across England and Wales youths and children are said to have carried out at least 5,000 child sex offences in the last three years, of which 351 were committed in Suffolk.

The national figures were released after Freedom of Information requests to police forces by the NSPCC. But the charity warns the true figure will be even higher as not all forces were able to provide relevant data.

The NSPCC is warning easy access to sexual material could be behind an increase in the number of children needing help.

Its policy advisor Claire Lilley said: “Any incidents like these are a real cause for concern and these figures should be ringing alarm bells with the authorities that this is a problem that needs to be tackled urgently.

“In some cases older children are attacking younger children, in other cases it’s sexual violence within a teenage relationship.

“Whilst more research needs to be done on this problem, we know that technology and easy access to sexual material is warping young people’s view of what is ‘normal’ or acceptable behaviour.

“We are treating an increasing number of children who have carried out online grooming, harassment in chatrooms and ‘sexting’.

“Children who are sexually abusive have often been victims of abuse, harm and trauma themselves. Exposure to this can make them think sexually abusing someone or being sexually violent is ok.

“But evidence shows that most young people who receive behaviour changing treatment early on, such as that offered by the NSPCC, will not continue to sexually abuse others or grow into adult offenders.

“If we are to tackle this growing problem and protect young victims, more needs to be done to identify and treat children at risk of sexually offending. And we must do more to shield young people from an increasingly sexualised society.”

Only 34 police forces in England and Wales issued their figures to the NSPCC.

A total of 5,028 sex offences were recorded where the perpetrator was under 18, with some as young as five or six.

The alleged crimes included rape and other serious sexual assaults, which were reported between 2009/10 and 2011/12.

Nearly all – 98% – of the 4,562 offenders were boys, and where the relationship was recorded at least three out of five of the victims knew the abuser.

More than one-third of the offences were said to have been committed by a family friend or acquaintance and one in five by family members.

These findings follow a report by probation inspectors which found that police, social workers and teachers were missing the warning signs that a child may sexually offend. The NSPCC’s Ipswich centre provides services to treat and reform children and young people from across Suffolk who exhibit signs of harmful sexual behaviour.

Anyone worried about a child should telephone the NSPCC’s helpline on 0808 800 5000. Children can contact ChildLine on 0800 1111.