The Conservative government triggered a “racialised” war on gangs that has stigmatised black youngsters and left Britain breaking its human rights obligations, Amnesty International has said.

In a report about a police list of gang suspects, called the gangs violence matrix, the human rights group alleged the list violated the human rights of the predominantly black youngsters on it.

The gang violence matrix is used by the Metropolitan police to identify gang members, and the force says it helps to thwart violence. Police in Greater Manchester and the West Midlands are understood to use similar lists. But Amnesty claimed the tactic missed the underlying causes of the rising violence on Britain’s streets.

Amnesty said the gang matrix stemmed from the Conservative response to the 2011 riots across England. “In the immediate days after the riots, then prime minister David Cameron promised a ‘concerted, all-out war on gangs and gang culture’ and within six months both the Home Office and the mayor’s office had announced flagship new anti-gang strategies, including the launch of a reconfigured [Met police] Trident gang command in London,” the report said.

The findings showed that of those on the matrix, 78% were black and 9% from other ethnic minorities. This compared with Met figures stating that 27% of those behind violence in London were black.

In London, 3,806 people were on the matrix, with 5% in the red category, assessed as having the highest risk of committing violence, and 64% in the green, the lowest.

Amnesty claimed the Met was putting people on the matrix in some cases because it mistook cultural preferences, such as the music people listened to, for criminality. It also claimed officers were using social media networks without a warrant to gather intelligence from those under suspicion.

Kate Allen, Amnesty International’s UK director, said: “The entire system is racially discriminatory, stigmatising young black men for the type of music they listen to or their social media behaviour, and perpetuating racial bias with potential impacts in all sorts of areas of their lives.

“Some police officers have been acting like they’re in the wild west, making the false assumptions that they can set up fake profiles and covertly befriend people online to monitor them without needing the appropriate search warrants.

“The mayor of London needs to dismantle the matrix unless he can bring it in line with international human rights standards.”

The Guardian first reported concerns the gangs matrix was overly targeting black youths in 2016, and on Monday reported that four out of 10 suspects were assessed as posing zero risk of committing violence, according to the police’s own assessments. Those assessments were carried out by a computer algorithm, the report said.

David Lammy MP: ‘Why are so many young black men and minors being arbitrarily criminalised in this way?’ Photograph: Stefan Rousseau/PA

Amnesty said the youngest person on the list was aged 12. A man called “Paul”, who applied for a job when he was 21 years old, said his criminal record check came back clean, but that he was still on the matrix. He said the only reason he could think of was an incident when he was aged 12.

The information commissioner is already investigating the gang matrix for any data law breaches.

Allen said Amnesty had stumbled on to the problems with the matrix during discussions with Met officers about the increasing role technology was playing in law enforcement. She said Met officers had alerted the human rights group by saying they themselves were concerned about the tactic.

Being entered on the matrix can blight the lives of those on it, even if they are not convicted of a criminal offence. Amnesty said the Met shared information with others in the public sector: “Data sharing between the police and government agencies means that this stigmatising ‘red flag’ can follow people through their interaction with service providers, from housing to education, to job centres, raising important questions about how this may impact their rights. Our report flags particular areas of concern across immigration, housing, education and employment.”

It concluded: “This report in many ways provides a case study of how a politicised ‘war against the gang’ has filtered down and become the crucial lens through which the Metropolitan police and other government services view and attempt to address serious interpersonal youth violence, gun and knife crime in London.

“In reality, as the Met points out, being in a gang or gang video is not, in and of itself, a crime. In fact, many of the signifiers used to identify ‘gang members’ reflect elements of urban youth culture and identity that have nothing to do with serious offending.

”This conflation of certain elements of urban youth culture with violent offending is heavily racialised.”

David Lammy, the Labour MP for Tottenham in north London, said of the report: “Why are so many young black men and minors being arbitrarily criminalised in this way when they have not committed a violent or serious offence?

“Why are young black men from the same neighbourhood automatically slapped with the gang label whereas the Bullingdon Club are not a gang?”

Lammy added: “This has resulted in a policing tool that essentially involves the profiling of urban young black men as gang members and violent criminals, which in turn has a serious impact not just on the life chances of these men but also for trust in the police and relations between communities and the police in parts of London like Tottenham.”

The Home Office referred questions about the matrix to the Met.

The Met said: “The style of music that someone listens to has no bearing on whether someone is placed on the matrix. However, evidence that someone is glorifying gang violence in a music video posted on social media can be used as an intelligence source.

“In relation to suggestions of potential racial disproportionality of the matrix, the MPS has actively engaged with David Lammy MP, Amnesty International and the information commissioner’s office to help understand the approach taken, and we remain committed to ensuring the safety of all Londoners, and especially those most at risk from gang and other violent crimes.”