Lockdowns gave criminal gangs time to strategise, charities have warned, with a wave of violence expected over the summer.

Young people caught up in gangs have told youth workers that the Covid lockdowns gave them the opportunity to plan "what they are going to do, and now they are going to go and do it", Kayleigh Wainwright, the director of the charity UK Youth, said.

London is on track to have its worst teenage homicide rate since 2008 after a spate of violence in recent weeks, including two boys aged 15 and 16 who were killed in separate stabbings in south London on the same day earlier this month.

"Our youth workers are definitely seeing more young people affected by violence and are expecting to see more over the holidays," Ms Wainwright said. "Obviously, that plays out differently if you live in a rural village or the Lake District compared to Manchester or London – it’s very different. But we are expecting an increase."

Craig Pinkney, a criminologist and urban youth specialist, told The Guardian that predictions made about youth violence at the start of the pandemic were starting to play out.

"The violence is going to erupt this summer. It’s like an explosion," he said. "Covid has really impacted people’s mental health and their social interaction. It’s almost like a melting pot. Young people don’t know what to do with their behaviours."

Tanayah Sam, the founder of TSA Sports in Birmingham, a not-for-profit organisation that engages young people through sport and media, said people had to accept that knife crime was going to get worse.

"I feel like most of the problems come from people not feeling safe in their own environment any more," he told The Guardian. "And I feel like the violence has been glamourised to the point where most people are doing it for clout, or for fame and status.

"Covid did make it worse because, in lockdown, there were more kids not in school. And in summer, when everyone was out partying, I saw more young people die in the space of a few months than I’ve ever seen before."