Children and young people who subject other children to harmful sexual behaviour are often themselves victims and should not be unnecessarily criminalised, according to a major inquiry into the causes and effects of child abuse.

The cross-party parliamentary inquiry, led by children's charity Barnardo's and Conservative MP Nusrat Ghani, was set up in February to investigate various elements of sexual abuse and children, including the role of internet pornography and mobile technology.

The report, released on Monday, calls for the government to work with schools and charities to draw up a national strategy for the prevention of sexual abuse among young people.

Ghani and Javed Khan, Barnardo's CEO, write in the report's introduction: "Abuse by adults is taboo, but abuse by children is doubly taboo. What do we call a child who sexually abuses their sibling, or school friend? Are they a mini sex-offender or a child in desperate need of help?"

The report says the current approach fails to consider the trauma that young offenders may have experienced – they are likely to have been victims of sexual abuse themselves – and overlooks that children and young people are "more likely than adults to achieve successful rehabilitation".

While the report concedes that some young people will pose a threat to wider society and should be dealt with by the criminal justice system, "young offenders should be treated as children first and offenders second".

Several children and young people have been arrested and charged for sexting and distributing images of themselves and others.

In 2014 a teenage couple received police cautions for sharing intimate pictures. In 2015 a 14-year-old boy was placed on a police database for sexting and a 17-year-old boy was jailed for blackmailing two younger boys over pictures they sent via Snapchat.

The report was keen to point out, however, that while it is technically illegal for anyone to distribute a compromising image of a child, sexting shouldn't necessarily be seen as harmful sexual behaviour and is often a normal part of a consensual, healthy teenage relationship.

In 2013–14, 4,209 people under 18 were recorded as having carried out sexual offences against other children and young people.

About 90% of young people identified as sexually abusing others are male, the report said.

However, chronic underreporting of sexual abuse hides the true figure: One study found that 82.7% of young people who experienced sexual abuse didn't tell anyone at the time.

The experts who contributed to the inquiry agreed that harmful sexual behaviour carried out by and to children was increasing.

The effects of pornography

The inquiry said that despite some evidence that access to pornography was linked to an increase in harmful sexual behaviour, it was "not easy to make a direct causal link between exposure to inappropriate media on the internet and the propensity to become an offender".

"The life experiences, social circumstances, support mechanisms and psyche of the

individual" are all factors in this, as well as someone's exposure to harmful content.

Nevertheless, children as young as 12 are being pressured to behave in a sexualised way.

The National Police Chiefs' Council is in the process of drawing up new guidelines on how police should deal with sexting by under-18s, although the current advice is already to minimise the risk of criminalisation.

The reoffending conundrum

More than £1 billion is spent each year by police forces in England and Wales investigating allegations of child abuse but more should be done to prevent abuse happening in the first place, the report says.

Children who sexually abuse other children are likely to have been victims of abuse themselves and are unlikely to pose a risk to the wider public – but, the report warns, often these children end up being unnecessarily stigmatised and criminalised as "sex offenders" at an early age, increasing the likelihood that they will reoffend.

Even in the most serious cases, the report calls for children to be given high-quality therapeutic support to minimise future offending.

The report makes clear that those likely to be victims of and carry out harmful sexual behaviour tend to have low social skills and high social anxiety, while a significant proportion have learning disabilities and/or autism spectrum disorder.