The police tactic of stop and search is increasing the likelihood of crime rather than preventing it, finds a report that paints a bleak picture of young men and boys snapping under the pressure of relentless checks sometimes multiple times a day.

Based on in-depth interviews with young Londoners named on the Metropolitan police’s controversial list of gang suspects – the gangs matrix – the report (pdf) also raises concerns about how the police’s “gang nominal” assessment has an impact on the lives of those listed.

The report for the charity StopWatch, a coalition of legal experts, civil liberties campaigners and others, heavily criticises the multi-agency approach in which information about those on the matrix is shared across public services, including education and housing providers. Concerns were raised about a lack of transparency and the sharing of information without the consent of the young people in question.

StopWatch’s report, Being Matrixed, draws on the testimonies of 15 Londoners aged between 17 and 32 who are on the matrix – which gives suspected gang members a score assessing how dangerous they are believed to be.

Anger at the frequency of searches was typified by the comments of one individual, who told researchers he had been stopped and searched hundreds of times. “I’ve got a conviction because I was stopped and searched three times in one day,” he said. “Now, if you’re stopped and searched three times in one day how are you going to feel? I flipped, I got done for public disorder and I was thinking I haven’t actually done nothing, you have stopped me three times in one day.”

Another claimed that being registered had hindered his employment prospects. He told the researchers: “I’ve applied for so many jobs within the youth sector, and they’ve told me that when they do like a CRB check, they told me that I’m on a ‘watch’. But they don’t say exactly what it is.”

Katrina Ffrench, the chief executive of StopWatch, said the findings added weight to evidence suggesting the matrix was not fit for purpose and should be reviewed by the mayor of London with a view to scrapping it.

She said: “To be on the matrix is to be literally blacklisted. It means that the young people on it are marked out for harassment and humiliation. It’s a highly racialised stigma that follows someone through every aspect of their life. Not only is the matrix completely ineffective at combating the crime it claims to want to tackle, our research suggests it makes crime more likely.”

A report this year by Amnesty International alleged the matrix violated the human rights of the predominantly black youngsters on it. Amnesty found that of those on the list, 78% were black and 9% were from other ethnic minorities.

The Met said it constantly reviewed and updated the processes involved in maintaining the matrix, as well as the individuals listed. It said the threshold for inclusion was high and inclusion happened only where the force had at least two corroborated pieces of tested intelligence. While the number of people listed had remained at about 3,500 since 2012, more than 4,000 people had been removed from the list.

Scotland Yard said it had altered the stop and search tactic, making it more intelligence-led, and that the arrest rate had risen from 8.4% to 18.5%. The force said an individual would not be stopped and searched purely and only through being on the matrix.