Kemi Badenoch has called for Axel Rudakubana's parents to be deported if they don't face criminal action after a public inquiry found they could have prevented the Southport attack.
The Tory leader said his father, Alphonse Rudakubana, and mother, Laetitia Muzayire, "knew their son was stockpiling weapons and planning an attack" but "chose silence" and "three little girls paid with their lives".
Alice da Silva Aguiar, nine, Bebe King, six, and Elsie Dot Stancombe, seven, were stabbed to death by Rudakubana, then 17, at a Taylor Swift-themed dance workshop on 29 July 2024.
Rudakubana, now 19, also tried to murder eight other children, class instructor Leanne Lucas and businessman John Hayes at The Hart Space in the Lancashire seaside town. He is serving a life sentence with a minimum term of 52 years.
In a 763-page report published on Monday, inquiry chairman Sir Adrian Fulford said Rudakubana would not have been free to kill had his parents "done what they morally ought to have done".
The retired High Court judge said if the full extent of their concerns had been shared with authorities "it is almost certain this tragedy would have been prevented".
He also blamed a string of agencies who failed to manage the risk, highlighting failures by police, the government's counter-terror Prevent Programme, social care and healthcare, and those involved with his education.
Merseyside Police said Rudakubana's parents, were granted asylum in the UK in 2003 after fleeing the Rwandan genocide, would not face criminal charges.
"There is no current legal duty on bystanders and/or parents to warn or report criminality," a spokesman said.
In a post on X on Wednesday Ms Badenoch said "they should face the consequences of their actions, or indeed their inaction".
"If they escape criminal charges on a technicality, the Government should deport them," she said, adding that the UK "must leave" the European Convention on Human Rights (ECHR) if the treaty stands in the way.
She said in a video: "These were people who were refugees in our country, they fled a horrific genocide, they know what violence looks like and when they saw that someone in their household was very likely to do the same to other people's children they did nothing.
"I think that is appalling, I think they have a lot of questions to answer.
"I think we should look at every possible avenue, to look at what we can do if not from a criminal side, then potentially even from an immigration side."
She also called on them to say sorry to the British public.
Both Rudakubana's parents, who are British citizens so cannot be deported, apologised when they gave evidence to the inquiry from remote locations, but have not commented publicly since the report was published.
Sir Adrian said they had faced "significant challenges" dealing with their son's behaviour but "ultimately failed" to report the risk in the week before the attack.
He also said individual parts of his report should not be used "to vilify or unfairly attack any of the individuals or the bodies for whom they work", urging the same for Rudakubana's parents.
He made 67 recommendations, including a Law Commission review into whether specified categories of persons ought to be under a legal duty to warn about, or a duty to report, the criminality of another.
(c) Sky News 2026: Badenoch calls for Axel Rudakubana's parents to be deported after damning Southport attack re
Fears government cash will come too late to save manufacturing jobs
UK military chiefs asked to find £3.5bn in savings - and get ready for war
Mark Kleinman blog | Mandelson's advisory firm collapsed owing taxman six-figure sum
'Corrosive complacency' - Lord Robertson tears into Starmer and Reeves in extraordinary intervention on defence spending
