More than 4,000 people in London have been recruited by drug gangs with networks spread across 41 counties in the UK, figures show.

Research released by Mayor of London Sadiq Khan shows thousands of people aged between 11 and 62 have been drawn into so-called county lines gangs.

The criminal networks deliberately target children and vulnerable adults to courier drugs from urban bases out to customers across the country, running phone lines to take orders.

Police chiefs say the gangs affect every force area in England and Wales and are linked to violent crime. It is estimated that around 15% of county lines activity originates in London.

The 4,013 individuals identified in the capital between January 2018 and April 2019 are linked to lines that spread across 41 counties in the UK, the most being in Norfolk, Hampshire, Essex, Sussex and Thames Valley.

Most were aged between 15 and 19 (46%), followed by 20 to 25 (29%). Just over a third, 34%, were under 18. Most were male (89%).

Within the capital, the boroughs that were home to the most individuals linked to county lines were Lambeth, Newham and Croydon, each with 200 to 300.

In 2018 Mr Khan gave £3 million over three years for a Rescue and Response programme to try to rescue under-25s who were lured into county lines.

The first year saw 568 young people referred to the programme including children as young as 11. Most were aged 15 to 18 (70%), and male (83%).

Of 568, 243 were referred to support services under the programme, of whom around 33 have been successfully drawn away from gang activity to date.

The rest either already had other support or a small number were put on waiting lists.

Those referred included one boy who was set up for exclusion from school by gang members who wanted to draw him into crime, while another who had witnessed domestic violence as a child was kidnapped and forced to work off a “debt” he had incurred when he got arrested.

Criminals offer young people and vulnerable adults money or drugs to lure them into gangs, approaching them in schools, pupil referral units, youth clubs, parks and fast food shops, as well as on social media and through gaming.

A common tactic is to trap them into debt by either staging a robbery or encouraging them to use drugs to run up a debt that they then have to work off.

County lines gangs use main train lines, coaches, taxis and hire cars rented from airports to travel around, sometimes forcing vulnerable adults to drive.

Drugs packages are taped to young people’s torsos or thighs, concealed in their underwear or swallowed, or sometimes hidden in empty games consoles.

Magnetic boxes can be stuck under cars, or hidden compartments created to conceal drugs, cash or weapons.

Mr Khan said: “County lines operate across the country, exploiting vulnerable young people and driving gang-related violence.

“Now, for the first time, through the Rescue and Response programme funded by City Hall, we are beginning to see the devastating scale of the impact with thousands of young people involved in lines reaching all corners of the country.”

The National Crime Agency, which jointly runs the National County Lines Coordination Centre with the National Police Chiefs’ Council, has estimated there are more than 2,000 individual deal line numbers in operation in the UK with annual profits for each in excess of £800,000.