Teenage boys are joining online gangs where they share sadistic and misogynistic material that fuels crimes including fraud, violence and child sexual abuse, the director general of the National Crime Agency has warned.

Offenders in online communities collaborate and compete to cause harm online and offline through cyber-attacks such as launching malware, ransomware or executing data breaches; fraud; extremism; grooming and blackmailing; serious violence; and child sexual abuse, according to the NCA, which leads the UK’s fight to cut serious and organised crime.

Online communities known as “Com” networks represent an “emerging threat”, reports of which have increased sixfold in the UK from 2022 to 2024. The agency’s analysts estimate that millions of messages in the UK and other western countries have been shared relating to sexual and physical abuse.

The NCA director general, Graeme Biggar, said: “These groups are not lurking on the dark web, they exist in the same online world and platforms young people use on a daily basis.

“Operating online clearly makes these offenders feel protected and out of reach but that is absolutely not the case. There have already been convictions; we and partners have made arrests in the UK and overseas, and further investigations are ongoing.”

The warning follows growing concerns about boys and young men in the online “manosphere”, after the Netflix hit Adolescence became the most talked about TV show of the year for its depiction of the relationship between online “incel” culture and real-world harm.

Keir Starmer responded to the show, saying there was “a problem with boys and young men that we need to address”, while the former England football manager Gareth Southgate warned of “toxic influencers”.

The NCA highlighted this emerging phenomenon in its national strategic assessment, an annual report that outlines the serious and organised crime threats facing the UK.

In the report, Biggar said criminals were exploiting “the societal shift to living more of our lives online”, and that this threat was diversifying, including “a growing overlap with online radicalisation to serious violence and extremism”, while artificial intelligence was making it easier to scale up offending.

The NCA and UK police have identified a number of cases in which girls, some as young as 11, have been coerced into seriously harming or sexually abusing themselves, siblings or pets. In some instances, victims have been groomed into offending, while some young girls have been encouraged to take their own lives.

Membership of these communities is loose and, although adults are involved, offenders are predominantly teenage boys who often share sadistic, misogynistic and nihilistic material on social media platforms, and who target those their own age or younger, the NCA found.

Evidence suggests these offenders are motivated by gaining notoriety and status from the harm they inflict and the depravity of the content they share. These networks share content relating to a diverse range of extreme belief systems that they use to justify violence.

Some offenders are also motivated by sexual gratification, while others seek to profit from criminality. The use of coercion and extortion tactics are common; for example, manipulating victims by grooming them, or convincing them they are in a relationship. This results in victims being fearful to come forward, contributing to under-reporting of offences.

Alastair Simpson, an assistant chief constable and national policing lead for child sexual exploitation and abuse, said undercover online officers played a “vital” role in tackling these networks.

“My message to anyone who is exploiting children online: remember that there is no space where criminals operate that we cannot go, and investigations into these networks have already begun,” he said.

The NCA said it was working with police, as well as tech companies, safeguarding agencies, psychologists and academic experts to better understand how young people become offenders. The agency also encouraged parents to speak to children about what they do online.

Jess Phillips, the minister for safeguarding and violence against women and girls, said the government was using “every lever at our disposal to make the UK a safer place for children online”, including by implementing the Online Safety Act, which has “some of the strongest laws in the world to protect children”.

“My message to tech companies is simple: this is your responsibility too. You must ensure your platforms are safe for children, so that we can protect the most vulnerable and put predators behind bars,” she added.

Responding to the report, Andy Burrows, the chief executive of the Molly Rose Foundation, said these groups posed a “deeply disturbing and sharply growing risk” to teenage girls.

“Despite being repeatedly warned of the threat posed by these groups, Ofcom has failed to introduce a single targeted measure to tackle disturbing suicide and self-harm offences. This glaring gap in its regulatory regime must be closed.

“The prime minister must now take decisive action to ensure the Online Safety Act is fit for purpose in the face of new online risks and the threat posed by the fluid ideologies that are fuelling this troubling wave of extreme violence.”

An Ofcom spokesperson said: “We’ve set out several specific measures that platforms can take to protect people from suicide and self-harm content. For example, our illegal harms codes of practice include reporting, moderation and takedown measures to tackle illegal suicide and self-harm material.

“We’ve also proposed additional protections for children, which we’ll be finalising next month, including measures on algorithms and age checks. And we’re already working on additional measures for consultation in the coming months, including the use of automated detection.”

• In the UK, the NSPCC offers support to children on 0800 1111, and adults concerned about a child on 0808 800 5000. The National Association for People Abused in Childhood (Napac) offers support for adult survivors on 0808 801 0331. In the US, call or text the Childhelp abuse hotline on 800-422-4453. Other sources of help can be found at Child Helplines International