The disproportionate number of deaths of black and brown people in incidents with the police shows that structural racism remains rooted in the fabric of British society, a panel of UN human rights experts has said.

The panel cited data from the Metropolitan police showing a disproportionate number of minority ethnic people – particularly those of African or Caribbean descent – dying due to excessive use of force by the state.

Noting that there had never been a successful prosecution of a police officer for a death in police custody, the panel said: “This points to the lack of accountability and the impunity with which law enforcement and state agencies operate.”

The warning from members of the UN human rights council comes before a 12-day visit to the UK by E Tendayi Achiume, the special rapporteur on racism, beginning on Monday. “The deaths reinforce the experiences of structural racism, over-policing and criminalisation of people of African descent and other minorities in the UK,” they said.

“Failure to properly investigate and prosecute such deaths results in a lack of accountability for those individuals and state agencies responsible, as well as in the denial of adequate remedies and reparation for the families of the victims.”

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The panel pointed particularly to the disproportionate use of stun guns. People from black and minority ethnic backgrounds were three times more likely to be subjected to the use of such weapons by police, they said.

The members added: “People of African descent with psychosocial disabilities and those experiencing severe mental or emotional distress reportedly face multiple forms of discrimination and are particularly affected by excessive use of force.”

A report last year by David Lammy, the Labour MP for Tottenham, found racial disparities across the criminal justice system. He has consistently said that young black men feel as though they are living in a police state and that a different standard of policing is applied to black youths, compared with whites.

At least five black men died in the UK after restraint by police last year: Edson Da Costa, 25, in Newham, east London; Darren Cumberbatch, 32, in Nuneaton, Warwickshire; Shane Bryant, 29, in Leicestershire; Rashan Charles, 20, in Hackney, east London; and Nuno Cardoso, 25, in Oxford.

Deborah Coles, director of Inquest, which supports the families of people who die in police custody, and which gave evidence to the UN panel, said: “The racial stereotype of the black man as ‘big, black and dangerous’, ‘violent’ and ‘volatile’, when woven into police culture and practice, can lead to the disproportionate and fatal use of force.

“There is a double-discrimination experienced by black people with mental ill health, with the stereotype of ‘mad, bad and dangerous’ too often informing treatment.”

A Home Office spokesperson said: “The government takes allegations of police racism very seriously and expects all allegations to be investigated thoroughly and perpetrators dealt with robustly. We are also clear that any use of force by the police must be necessary, reasonable and proportionate.

“Every death in police custody is a tragedy. In October 2017, we published a major independent review into deaths and serious incidents in police custody alongside our response, setting out the steps we are taking to address the recommendations and the progress made to date.”