A police gangs database containing details of 1,500 people who score zero for risk of violence is under investigation by the data watchdog.

The Met Police’s Gangs Matrix holds information on around 3,800 people, around 40 per cent of whom have a harm score of zero.

A report by Amnesty International claims the database breaches international human rights law.

But the Met says it is designed to save lives.

Amnesty director Kate Allen said: "There is clearly a huge problem with knife crime violence at the moment in London, but the Gangs Matrix is not the answer. It's part of an unhelpful and racialised focus on the concept of gangs. Put simply, it's the wrong tool for the wrong problem.”

Amnesty found that the number of black men on the Matrix is disproportionate. Figures from July 2016 showed that 87 per cent of the people listed were black, Asian and minority ethnic, and 78pc were black.

The report claims being on the Matrix could affect access to services such as housing, education and the job centre.

Researchers heard some families were threatened with eviction if a young person did not change their behaviour, and one was sent an ultimatum more than a year after their son had died.

The Met says none of this should happen as a result of the database.

The force gathers various intelligence including history of violent crime, entries on social media and information from bodies including local councils to identify gang members, then uses an algorithm to calculate a risk of harm score.

ICO Deputy Commissioner for operations, James Dipple-Johnstone, said: "We’re considering how the database is used and if any aspects of it constitute a breach of the Data Protection Act.

"At the conclusion of our investigation we will communicate any resulting recommendations and enforcement actions."

The Met says the aim of the matrix is to stop young people being killed.

A spokesman said: “Some young people identified as part of a gang, may not yet have been drawn into gang violence. These individuals will be offered support to divert them away from activity that may result in either violent offending or them becoming a victim.

“Any action taken by partner organisations should not be instigated solely on a person's name being on the gang matrix.

“Similarly, court sentencing outcomes should not be influenced by the gang matrix.

“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.”