Policing could be driven back to the 1960s by false claims officers are biased against white people, the leader of Britain’s black officers has said.

Ch Insp Andy George, president of the National Black Police Association, spoke out amid growing concerns that politicians such as Nigel Farage were stoking tensions around the murder of teenager Henry Nowak by making baseless and provocative claims.

Senior figures in policing were among those who pushed back against his assertion that the handcuffing of Nowak by officers in Southampton last December after he had been stabbed amounted to two-tier policing and a bias against white people.

They also denounced Farage for saying the response to the killing demanded “cold rage”.

Keir Starmer accused the Reform UK leader of ignoring the wishes of the dead teenager’s family and called the Reform leader’s actions “unforgivable”.

Nowak’s father Mark had condemned the “inhumane and degrading” treatment of his son by police.

But he added: “We do not want his death to be used to create further division, hatred or tension. We want his story to help make our streets safer for everyone.”

Hampshire’s chief constable Alexis Boon, whose officers are under scrutiny over the way they dealt with the incident, on Wednesday apologised for the way Nowak had been arrested and handcuffed. He added: “I’m so sorry you’ve had to go through this.”

The killing of Nowak, an 18-year-old university student, has sparked a nationwide debate about policing.

The teenager was stabbed last December by Vickrum Digwa, who falsely claimed he had been racially attacked by him.

In fact, Digwa had stabbed Nowak repeatedly, but officers arriving at the scene treated the student as a suspect. He was handcuffed and put under arrest, despite telling officers he had been stabbed and could not breathe.

The Guardian has learned that police chiefs have ordered the nationwide increase in intelligence gathering about potential violence believed to be linked to far-right protests, with 11 officers injured after clashes in Southampton on Tuesday.

George said bogus claims from politicians such as Farage and far-right activists that policing is biased against white people could set back efforts to end systemic, longstanding prejudice against black people.

He said: “There is a danger of policing going back to a time long before Stephen Lawrence’s murder, to the 1960s and 1970s, because of the attacks from the far right which have been growing over the past few years, and which are becoming more mainstream.”

In the House of Lords, Lady Lawrence, who fought police for justice after they failed her murdered son Stephen in 1993, said: “My condolences goes out to Henry Nowak’s family. I think what’s happened with him should never have happened. And the police should be at fault for what happened on that night,” she said.

Body cam footage of the student’s final minutes is accepted by police sources to be “traumatic”.

The incident is being investigated by policing watchdog the Independent Office for Police Conduct.

Sir Andy Cooke, who stood down in April as chief inspector of constabulary, told the Guardian he found no evidence of anti-white bias during his time scrutinising all forces in England and Wales.

He said politicians such as Farage were trying to “exploit” the Nowak case “to boost their political fortunes” and worsen community tensions.

Cooke, who was appointed by the Conservatives and won praise from both main parties, said: “Throughout my five years at the inspectorate, I found no evidence at all to support any claim there was an anti-white bias in operational policing.

“At a time when there is disquiet in some communities, this is no time to play politics with community tensions, particularly off the back of such a distressing incident that caused so much pain to the family of Henry Nowak.

“This should be a period of time where politicians respect the family’s wishes and do not try to exploit such a tragic and painful situation to boost their political fortunes.”

His intervention came as Southampton recovered from violence after protests led by far-right activist Tommy Robinson, whose real name is Stephen Yaxley-Lennon. That followed Farage’s calls for “rage” at how Nowak was treated by police.

He had been stabbed by Digwa after a dispute flared out of control, but officers were unaware how seriously he was injured, ignored his pleas he had been stabbed for about three minutes and handcuffed him.

One senior police source said police believed politicians were attempting “to stoke up tensions for political gain”, making clear they meant Farage and Robinson, as well as some Conservatives, and “they were reckless about whether their comments would lead to trouble on the streets”.

In the House of Commons both Starmer and Kemi Badenoch, the Conservative leader, warned against divisive rhetoric, with the prime minister condemning Farage exploiting the tragedy for political gain.

“This is a time for serious work, not rage,” Starmer said, a response to Farage’s call to respond to the case with “pure, cold rage”.

Farage used a question to claim the UK was “living under two-tier policing”, saying this had led to “the anger that you saw spilling out in Southampton last night”.

Starmer called the Reform UK leader’s comments “unforgivable” and said: “A grieving family have asked us not to respond in the way that the leader of Reform has responded … His response has been to appeal for rage – rage. That’s his response to a father who has lost his son and asked for that not to happen. Exploiting this tragedy to create grievance and division would be wrong in any circumstances, but to do it when the family are expressly saying please don’t is unforgivable. It shows exactly who he is.”

Government and police are discussing a review of police promises on tackling racial bias against black people, with ministers convinced some of the wording was clumsy and open to attack.

In the Portswood area of Southampton, where anti-police protesters clashed with police on Tuesday night, politicians and residents criticised the violence.

Satvir Khan, the MP for Southampton Test and the first woman Sikh to become a UK government minister, said she needed a security guard when she visited the area because she had received death threats.

Community leaders said there had been an increase in hate aimed at Sikh people and some were changing their routines to avoid being targeted and there were extra police patrols around Sikh buildings.

Meanwhile, a former police officer was forced to flee to a safe space after she was falsely accused online of being involved in the arrest of Nowak.

Christi Hill, who served as a police constable for 12 years, has criticised social media and AI platforms, including Elon Musk’s Grok, for spreading the false claim that she was one of the officers who arrested Nowak. She said she had left the police more than a year before the murder.

Boon, Hampshire’s most senior officer, rejected claims of anti-white bias and said: “I don’t accept the term of two-tier policing, I don’t recognise it.”

He said some of the criticism directed at Hampshire constabulary has been “unfair”, in an interview with broadcasters.