Sir Keir Starmer has accused Nigel Farage of exploiting the death of Henry Nowak to create "grievance and division", as the political fallout from the teenager's murder saw angry exchanges in the Commons.
It comes after the Reform UK leader suggested the British public react with "pure, cold rage" to the actions of police, who arrested the 18-year-old as he lay dying after his killer falsely accused him of racism.
Speaking during PMQs, Farage repeated his claim that the incident was the result of "two-tier policing", citing anti-racism guidance issued by police bosses.
The prime minister rejected this, adding that politicians needed to respond to the case with "serious work, not rage".
Vickrum Digwa, 23, was jailed for life with a minimum of 21 years on Monday for Nowak's murder in Southampton last December.
Digwa stabbed Nowak with a large blade he claimed to carry as part of his Sikh faith, before falsely claiming to police he had been the victim of a racist attack - leading officers to initially arrest the white teenager, rather than his killer.
Bodycam footage released this week showed Nowak repeatedly telling officers he had been stabbed as he lay dying in handcuffs.
The incident, which is being investigated by the policing watchdog, prompted a wave of political reaction on Monday, including a video clip filmed by Farage in which he said the police response was evidence of "two-tier Britain," and called for an end to "anti-white prejudice".
He added: "Henry's family have responded to this in just the most extraordinarily dignified way. But I suggest the rest of us respond to this with pure, cold rage."
Speaking in the Commons, Farage repeated his insistence the case showed "two-tier policing", arguing that anti-racism guidelines issued to officers had led forces to treat "different ethnic groups in different ways".
He warned that violent protests in response to the case could get worse if the public loses trust that they will be "treated fairly" by officers, as he was repeatedly heckled by other MPs to condemn clashes with police on Monday evening.
In reply, the prime minister said he had been "shocked" by Farage's response to the case, and accused him of disregarding pleas from Nowak's family that his death should not be used to stoke division in society.
"A grieving family have asked us not to respond in the way that the leader of Reform has responded," he told MPs.
"My response - and the response of others, to be fair - has focused on the lessons to be learned, so we can deliver justice.
"His response has been to appeal for rage. Rage – that's his response to a father who's 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."
It comes as the organisation representing police bosses in England and Wales said it would review the language in a document, the Police Anti-Racism Commitment, published last year in the wake of a policing action plan in 2022.
The document, which includes a line saying police should not aim to treat everyone "the same" as they aim to produce "equality of policing outcomes" for different ethnic groups, has come under scrutiny in the wake of Nowak's murder.
Earlier, Policing Minister Sarah Jones said she thought the language in the document was "wrong" and it "gives the wrong impression".
But she insisted it was a "values document" and not form "the basis of any training or any police activity.
