Britain faces a new threat of terrorism from “extreme violence carried out by loners, misfits, young men in their bedrooms” following the Southport murders, the Prime Minister has said. Axel Rudakubana, 18, pleaded guilty on Monday to murdering three girls at a Taylor Swift-themed dance class in Southport, Merseyside, in July.

Despite contact with state agencies such as Prevent, aimed at countering terrorism, authorities failed to stop the attack which claimed the lives of Alice da Silva Aguiar, nine, Bebe King, six, and Elsie Dot Stancombe, seven. Home Secretary Yvette Cooper announced an inquiry into the case on Monday evening, saying the country needed “independent answers” on Prevent and other agencies’ contact with the “extremely violent” Rudakubana and “how he came to be so dangerous”.

Addressing the nation on Tuesday, Sir Keir Starmer said: “The predominant threat was highly organised groups with clear political intent – groups like al Qaida. That threat, of course, remains but now alongside that we also see acts of extreme violence perpetrated by loners, misfits, young men in their bedroom accessing all manner of material online – desperate for notoriety, sometimes inspired by traditional terrorist groups, but fixated on that extreme violence, seemingly for its own sake.”

The PM continued: “My concern in this case is we have clearly got an example of extreme violence, individualised violence, that we have to protect our children from and our citizens from. It is a new threat, it’s not what we would have usually thought of as terrorism when definitions were drawn up, when guidelines were put in place, when the framework was put in place and we have to recognise that here today.”

He said the law and framework for responding needed to be appropriate to the “new threat” and whatever changes were necessary in the law would be made.

Sir Keir continued: “I do think it’s new. You’ve seen versions of it in America with some of the mass shootings in schools.

“It is not an isolated, ghastly example. It is, in my view, an example of a different kind of threat and that is why I’m absolutely so determined that we will rise to that challenge and make sure that our law, our response, is capable, appropriate and can deal with that sort of threat.

“But that is my concern, that is my thinking that this is a new threat – individualised extreme violence, obsessive, often following online viewing of material from all sorts of different sources.

“It is not a one-off. It is something that we all need to understand and have a shared undertaking to deal with within our society.

“That is not just the laws on terrorism, the framework on terrorism, it’s also the laws on what we can access online.

“We still have rules in place in this country about what you can see at a cinema and yet online you can access no end of material. We have to ensure that we can rise to this new challenge and that is what I’m determined to do.”

Addressing the inquiry which was announced on Monday, Sir Keir said failures of state institutions in Rudakubana’s case “frankly leap off the page”.

He said: “As part of the inquiry launched by the Home Secretary yesterday, I will not let any institution of the state deflect from their failure – failure which in this case, frankly, leaps off the page.

“For example, the perpetrator was referred to the Prevent programme on three separate occasions – in 2019 once and in 2021 twice.

“Yet, on each of these occasions, a judgment was made that he did not meet the threshold for intervention – a judgment that was clearly wrong and which failed those families. And I acknowledge that here today.”

Mr Justice Goose said Rudakubana, of Banks, Lancashire, will be sentenced on Thursday.

He is not expected to receive a whole life order because he was 17 at the time of the murders. The measures can normally only be imposed on criminals aged 21 or over, and are usually only considered for those aged 18 to 20 in exceptional circumstances.

Rudakubana, who was born in Cardiff, also admitted the attempted murders of eight other children, who cannot be named for legal reasons, class instructor Leanne Lucas and businessman John Hayes.

He further pleaded guilty to possessing a knife on the date of the attack, production of a biological toxin, ricin, on or before July 29, and possession of information likely to be useful to a person committing or preparing to commit an act of terrorism.

The terrorism offence relates to a PDF file entitled Military Studies In The Jihad Against The Tyrants, The Al Qaeda Training Manual, which he is said to have possessed between August 29 2021 and July 30 2024.

The ricin, a deadly poison, and the document were found during searches of the home in Old School Close which he shared with his parents, who are originally from Rwanda.

Documents about Nazi Germany, the Rwandan genocide and car bombs were found on Rudakubana’s devices during police searches of his home.

Sources said the material showed an “obsession with extreme violence” but there was no evidence he subscribed to any political or religious ideology or was “fighting for a cause”.

Unrest erupted across the country in the wake of the Southport attack, with mosques and hotels used for asylum seekers among the locations targeted.

In the hours after the stabbing, information spread online which claimed the suspect was an asylum seeker who had arrived in the UK on a small boat.

The day after the attack, thousands turned out for a peaceful vigil in Southport, but later a separate protest outside a mosque in the town became violent, with missiles thrown at police and vans set on fire.

More than 1,000 arrests linked to disorder across the country have been made since the attack, and hundreds have been charged and jailed.