Cocaine use at “middle-class parties” is helping to fuel drug-related gang violence on the streets of London, Sadiq Khan has warned.

London’s mayor said recreational drug use was not a “victimless crime” and he had seen evidence from authorities of a clear link between cocaine consumption and rising violence in the capital.

Khan called for action to be taken against people who buy the drug at “middle-class parties”, alongside a crackdown on gang members.

The mayor, answering questions on his LBC radio phone-in show, said: “There is a definite link, which has been shown to me by the police, of drugs and criminal gangs and knife crime and crime going up.”

He continued: “We have got to make sure we take action among those young people who are involved in criminal gangs as well as those who are buying them at middle-class parties.

“There are some Londoners who think it is a victimless crime, taking cocaine at ‘middle-class parties’. We need to make sure Londoners realise there is no such thing as a victimless crime.”

He added: “Some of the young people being knifed on our streets in London, some of the young people losing their lives is because they are involved in criminal gangs who are lower down the food chain in relation to drugs.”

Taking cocaine at ‘middle-class parties’ is not a victimless crime, says mayor. Photograph: DAVID COLE / Rex Features

The mayor’s comments came after the justice secretary, David Gauke, said in May that middle-class people who take cocaine “should feel a degree of guilt and responsibility” when they see stories of teenagers being murdered in Hackney, east London.

Khan, who campaigned for a remain vote in the EU referendum, said Brexit could make tackling the illegal drug trade trade more difficult.

“The drugs come from overseas and the idea that we will be more effective at fighting crime by leaving the EU – by not having the security arrangements with the EU – is ridiculous,” he said.

In May, Simon Kempton, who leads on drug policy for the Police Federation, also said middle-class drug users were to blame for the drug trade and related violence.

Speaking at the federation’s conference in Birmingham, he said: “‘The only reason gangs are into drugs is because people want to buy them, and a big part of that is not street-level users. Street-level users are a problem because they steal to fund their habit but on their own they will not support an organised crime group.

“The big market is people with money to spend and they are often oblivious to the misery they cause because it is not on their doorstep. Middle-class drug users do not come across the radar of police because they are consuming it behind closed doors.”