Nearly 10,000 Islington residents are thought to be addicted to crack, heroin, methadone or alcohol.

Figures in a new report estimate that around 2,750 people are hooked on crack cocaine or opiates, with a further 6,800 dependant drinkers.

It means approximately one in 20 people in the borough could be addicted to drugs or alcohol.

The statistics come from a report by NHS North Central London for a health scrutiny committee meeting on Tuesday, detailing how to improve drug and alcohol treatment services in Islington.

In 2010, the government changed how successful treatment was judged and a patient now has to be ‘clean’ for six months.

Islington is well below the national average against this new benchmark – 11 per cent compared to 15 per cent nationwide – although it does better compared with similar boroughs.

Jess McGregor, senior commissioning manager for substance misuse and prison health care, said: “It has to be stressed that these figures really are estimates, especially the dependant drinkers, which rely on possibly flaky data. We knew we needed to improve in some areas, but thought we were making progress. We were quite surprised to find we weren’t.

“This report doesn’t focus on the things we do well, like keeping people in treatment, reducing drug use and harm to users’ health, but we are all clear on what we need to do and we are excited and motivated.”

The report identifies several areas for improvement, but Ms McGregor highlights more support for heroin or methadone users, who are less likely to end up drug -free.

“It’s the biggest challenge but could make the biggest difference,” she added.

The report also stresses more provision is needed for people aged 18 to 24, including separate treatment for the age group. One member of staff from a unit said: “Putting 19-year-olds in with hardcore crack addicts is not appropriate or safe.”

The report also called for support for youngsters on softer drugs as it can often lead to addiction to harder substances. A member of a carer focus group said: “Cocaine forms part of a normal night out in Islington. People don’t see it as a problem but it can lead to addiction.”