Thuggish gang members judged a low risk to the public, youngsters with drug and alcohol problems left untreated, and high re-offending rates are among the failings of Islington’s Youth Offending Service (YOS), a damning report has revealed.

An investigation by Her Majesty’s Chief Inspector of Probation found the YOS, which stops delinquent teens from re-offending, rated poor – the lowest ranking – in four out of six categories.

The document highlights limited and delayed interventions, a reliance on the offenders’ version of events and a failure to recognise dangerous and vulnerable youngsters.

One case study described a 14-year-old gang member who whipped a victim from a rival group with a belt buckle and tried to bite the arresting police officer before being involved in a group fight where he chased his victim with a knife.

Although a subsequent stop and search resulted in an arrest for possessing a weapon, his risk of serious harm level was judged to be medium. The board said it should have been high.

Another case involved a 16-year-old who had stolen a moped and been seriously injured in a collision. His friend had died in a similar crash but the teen continued to steal mopeds and place himself and others at risk, yet was judged low vulnerability.

And for another young person with a long history of being bullied, which led to his offending, it took six months to start addressing the problem.

For phone snatches, one of the borough’s most prolific crimes, there was no specific plan of action. One young person had committed 93 offences, many stealing mobile phones, but was not referred to any support.

Cllr Joe Caluori, Islington Council’s executive member for children and families, said: “We agree with the main inspection findings and will use these in the next stage of our improvements, as we take action to address the key offending behaviours in the borough.

“We will continue to make sure young people serve their sentences, which is highlighted in the report as our strongest area of practice.

“The council and its partners are committed to addressing the findings of the inspection. We will continue to work closely with the Youth Justice Board, police and probation and are confident that we can accelerate our improvements and provide good quality services that prevent crime and tackle re-offending.”

It’s not the first time Islington’s YOS has come under fire; in 2011 inspectors found the team was below the national average in its efforts to safeguard the youngsters, protect the public and reduce the risk of re-offending,

An investigation by the Gazette in the same year revealed young criminals were convicted of 130 offences including violence, robbery and theft while using the service.