The number of young Londoners on a “discriminatory” Met Police watchlist has been halved following a review by the Mayor of London.

The Met’s Gang Violence Matrix was established in 2011 following the London riots and is used to identify individuals deemed to be at risk of committing or becoming involved with gang-related violence.

But the tool has been criticised by international human rights groups including Amnesty International and Liberty, the latter of which is pursuing legal action against the Met over its use of the matrix.

Research from Amnesty found that the database disproportionately targets young Black men and led to increased incidents of police harassment and victimisation, while a review led by Labour MP David Lammy found that many of the people on the list were “mislabelled” as gang members and were unaware of how to clear their names.

Following the latest review by the Mayor’s Office for Policing and Crime (MOPAC), the Met has taken the decision to remove 1,200 people deemed to be “low risk” from the database.

According to the latest figures, there are now 1,933 individuals listed on the matrix, a decrease of almost 50 per cent from August 2017 when the figure peaked at 3,881.

Mayor of London Sadiq Khan said that the “comprehensive overhaul” of the Gang Violence Matrix should “help increase the degree of confidence all of London’s diverse communities can have in the Met”.

He said: “As a direct result of the police acting on the recommendations, the Matrix database is now more effective and more evidence-based than ever before.

“We know that gang-related violence still accounts for a significant proportion of the most serious crime in London and the Matrix is a necessary enforcement tool as well as a means to support and intervention, but it’s vitally important that the police continue to evaluate how it is used. It’s something the new Met Commissioner and I have committed to improving together in order to build a fairer and safer London for everyone.”

Met Commissioner Sir Mark Rowley said he recognises that the matrix should be “redesigned”, but stressed that “the Met does need to use intelligence and data-led tools in order to help protect the public from perpetrators of violence”.

He said: “We know that young men; and in particular young Black men, continue to be over represented on the Matrix. Sadly, there is a reality that levels of violent crime do disproportionally affect young Black men – both in terms of victimisation and offending and our tactics do need to be targeted so we can protect those most at risk. However, it is not appropriate that the Matrix further amplifies this disproportionality. As an immediate response, we are removing all the lowest risk individuals. This represents 65 per cent, or more than 1,100 people.”

With Liberty’s legal challenge reaching the courts later this year, a representative said it was “right” for the Met to remove low-risk individuals from the Matrix but that it “does not go far enough”.

A spokesperson for Liberty said: “Being on the matrix can have a devastating consequence on your life, from increased stop and searches to having private data shared with schools and housing providers that affects your education and accommodation statuses.”

The Network for Police Monitoring (Netpol) said: “The racist gangs matrix had real-life consequences – so-called ‘lawful harassment’ by police – for those who unlawfully ended up on the list. There’s no indication anyone has even been told they have now been removed from it. This in itself is a scandal.”