The police and crime commissioner for Hampshire is leading calls for a review of religious exemptions on the carrying of knives after Henry Nowak, 18, was murdered by a man carrying a “Sikh dagger” in Southampton.

Donna Jones described the stabbing of the university student as a “national tragedy” and said she was writing to the prime minister, Keir Starmer, about the issue.

Vickrum Digwa, 23, was jailed for life on Monday for stabbing Nowak five times last December.

Hampshire police released footage from body-worn cameras showing Nowak being handcuffed despite repeatedly telling police officers that he had been stabbed. At one point an officer tells him: “I don’t think you have, mate.”

Digwa, who falsely claimed he had been racially abused and attacked by Nowak, is seen lying to police that the teenager knocked his turban off and caused an eye injury.

Jones said: “Henry was falsely accused of racially aggravated assault as he lay dying on the ground, while his attacker stood by denying the violent act he had inflicted upon him.

“It is devastating the officers did not believe Henry when he said he’d been stabbed and couldn’t breathe. His death is a national tragedy. Central to this incident is the fact that Vickrum Digwa was able to carry a knife in public because there is an exemption for those who observe the Sikh faith to carry ceremonial daggers.

“I intend to write to the prime minister to request a national review of the laws concerning the carrying of bladed articles under religious exemptions.”

The Cabinet Office minister, Nick Thomas-Symonds, said the footage was harrowing, telling the BBC: “The conduct of the police at the scene is shocking.”

But he did not suggest the UK government would examine the exemption allowing Sikhs to carry knives.

He said: “There is an exception in terms of carrying bladed articles in public places for particular religious and ceremonial reasons.

“And whilst, of course, we’ve been tightening up the law, we’ve banned things like terrible zombie knives, we’ve tightened up the law in terms of online purchasing of knives, it’s not about looking, I think, more broadly at that particular exception.

“If you look at what the judge said in this case, the judge actually said that the minute that this perpetrator removed the blade from the sheath, you can forget any sense of there being some sort of exception to the law.

“And he also said the fact that this perpetrator was willing to use a bladed article was an abuse of the privilege that Sikhs and indeed other religions have. It was something that made this case worse because of that abuse of that privilege.”

In a statement issued via the Sikh Press Association, members of Digwa’s family expressed sorrow for the Nowak’s family’s suffering. They said: “We love Vickrum. We will continue to love him. That love does not stand in opposition to the sorrow we feel for the Nowak family.

“We apologise to the Sikh community for our son’s actions which have unfairly brought the community into disrepute. We ask that this tragedy is not used by anyone to inflame division or hostility towards any community.”

In what he billed as an emergency address to the nation, the Reform UK leader, Nigel Farage, said people should respond with “pure cold rage” and called on the attorney general to review the minimum term Digwa will serve – 20 years and 190 days – before he can be considered for parole.

He said: “An accusation of a racial slur was treated more seriously than an act of murder.”

Hampshire police have apologised for their actions, which received global attention after being criticised by the owner of X, Elon Musk. The police watchdog, the Independent Office for Police Conduct, is investigating.

Speaking outside court, Nowak’s father, Mark, criticised how police had treated his son, whom he described as friendly and inclusive.

He said: “Henry did not die with dignity. He did not die with the care he deserved. We hold Vickrum Digwa solely and 100% responsible for the brutal murder of our son. But Henry should not have died on the streets of Southampton in police custody. The way he was treated was inhumane and degrading.”

Nowak added: “We are calling on the government to treat knife crime as the national emergency that it is.”

The prosecution told the jury at Southampton crown court that while Digwa was wearing a small kirpan (a ceremonial sword or dagger worn by initiated Sikhs) under his clothing around his neck, which met his religious obligation, he also chose to carry the much larger knife.

Judge Mousley KC described the weapon Digwa was carrying as a “large Sikh dagger”. He said practising Sikhs were allowed to be in public with a bladed article, but said that privilege came with huge responsibility.

The Council of Southampton Gurdwaras, which represents Sikh people in the city, expressed “profound sorrow” over Nowak’s death.

In a statement, it said: “We have been struck by the dignity and moral strength shown by Henry’s family, through all of the online noise from third parties.”

The statement continued: “Digwa’s actions were in direct contradiction to Sikh teachings and values that have guided Sikh communities for more than five centuries, including in Britain for over 150 years. His conduct is wholly unrepresentative of Sikhs in Southampton, the UK, or anywhere else. We condemn it unreservedly.

“Crimes of this nature must not be used to foster division between communities or to weaken the bonds that hold society together. Such division is contrary to the principles of Sikh teaching, which emphasise respect, responsibility and living alongside others in mutual understanding, irrespective of difference, as one large integrated community.”

The body-worn footage was shown during the trial. Hampshire police said it had talked with Nowak’s family about its release.