Hundreds of thousands of teenagers are afraid to go out because of the violence they see on their social media feeds, a major study of children in England and Wales has found.

One in four teenagers who see real-life violence, including fist fights, stabbings and gang clashes, online are being served the clips automatically by algorithmic recommendation features, according to the study done by the Youth Endowment Fund (YEF) and shared with the Guardian. Only a small minority actively searched for the violent content.

TikTok is the most likely place for teenagers to encounter real-life violent content, followed by X, according to the survey of more than 10,000 13- to 17-year-olds. New laws are to come into effect from next spring under which tech companies will face large fines if they fail to deploy age checks to prevent children seeing harmful or age-inappropriate content, including serious violence.

Eight out of 10 of those who saw weapons in social media clips said it made them feel less safe in their local area, and 68% - the equivalent of around 760,000 teenagers – said it made them less likely to go out. One in nine children had seen zombie knives or machetes on social media.

“Anyone working for Tiktok or X should feel ashamed reading this,” said Jon Yates, the chief executive of YEF. “You should feel guilty … and then you should turn that into action and do something about it.”

Jendayi Selassie, a social action coordinator for the Bringing Hope charity in Handsworth, Birmingham, confirmed the effect. After a spate of stabbings and a shooting in the city one weekend recently, she said: “A lot of the problems happening now are because something happened on social media …. They live on these devices and get a lot from it. Definitely more that is bad [than good].”

Clips of fights and chases, and songs boasting about violence were routinely shared on social media, increasing teenagers’ anxiety and also bruising pride in a way that led to more violence, young people involved with the charity said.

The amount of violence the teenagers see appears to far outweigh the actual risk of violence. Only one in 20 teenagers said they carried a weapon, but one in three saw weapons on social media.

Yates said: “We have a real problem with violence in the country, but social media makes it even more scary than it needs to be and it makes it worse. And you can see [from the survey] that children being afraid will lead to some children being more likely to carry a knife.”

Smaller, but still significant, proportions of teenage users of Facebook, Snapchat and Instagram (33%-31%) also saw violent content.

According to TikTok, more than 96% of videos violating its prohibition of violent threats, promotion of violence, incitement to violence, or promotion of criminal activities are removed before being reported. It said it restricts potentially inappropriate content for younger users, who can also enable a “restricted mode”. X did not respond to a request for comment.

The findings suggest social media algorithms may be driving some teenagers to actual violence themselves, with a sample equivalent to around 330,000 young people in England and Wales saying social media played a role in them perpetrating a violent incident.

Selassie said social media had helped make gang violence part of “a culture”, which extended to more affluent areas, rather than it being a function of poverty and inner city criminality.

Black boys were the most likely to have seen violent content online (78%) while white children were less exposed (69%), the survey found. Children with special educational needs were almost as likely to have seen violence as black boys – 10 percentage points more than children without SEN.

The secretary of state for science and technology, Peter Kyle, last week pushed the regulator Ofcom to be more assertive in taking on social media firms and ensuring safety was “baked in” to their systems.

Kyle said: “When I speak to mental health doctors and consultants, there’s no question that children’s vulnerabilities are being exploited, or discovered and exploited, by online activity.”

Amid a debate about whether social media should be banned for under 16s, the YEF research found that 32% of boys support banning the use of mobile phones on the way to school, compared with 21% of girls. Similarly, 36% of boys support bans during school breaks, compared with 27% of girls. The figures appear to reflect the role of social media in inflaming “beefs” between gangs and other groups outside the classroom.

“Children going out less, and young people going out less, makes them more anxious, makes them more likely to be lonely, and makes them less happy,” said Yates.

Meta, which operates Facebook and Instagram, pointed to its policy of removing content that incites or facilitates severe violence and said it took action on nearly 15m pieces of violent and graphic content in the three months to June, 99% of which were found before they were reported.

A spokesperson for Snapchat said: “We strictly prohibit content that encourages, threatens or graphically depicts violent or dangerous behaviour on Snapchat. If we find this content, or if it is reported to us through our confidential in-app tools, we will remove it, and take appropriate action.”