There are “grave questions to answer” over the state’s failures to protect the three young girls murdered in the Southport attack, Prime Minister Sir Keir Starmer has said.

On Monday, Axel Rudakubana pleaded guilty to the murders of Bebe King, 6, Elsie Dot Stancombe, 7, and Alice da Silva Aguiar, 9 who had been attending a Taylor Swift-themed dance class.

Government sources have told the BBC that Rudakubana had been referred to the government’s counter-terrorism Prevent programme several times prior to the attack in Southport.

In a statement, Sir Keir said “Britain will rightly demand answers” adding: “We will leave no stone unturned in that pursuit.”

“At the centre of this horrific event, there is still a family and community grief that is raw; a pain that not even justice can ever truly heal,” he said.

“Although no words today can ever truly convey the depths of that pain, I want the families to know that our thoughts are with them and everyone in Southport affected by this barbaric crime.

“The whole nation grieves with them.”

Conservative leader Kemi Badenoch has also said there are questions to answer about the case.

In a social media post, she said: “We will need a complete account of who in government knew what and when. The public deserves the truth.”

At a court hearing in December last year, not guilty pleas had been entered on behalf of Rudakubana, however on Monday morning he admitted to sixteen charges including the murder of the three girls on 29 July last year.

He also pleaded guilty to the attempted murders of eight children and two adults, possession of a knife on the day of the murders, producing a biological toxin, ricin, and the possession of an al-Qaeda training manual – a terror offence.

The BBC has been told that before the attack, Rudakubana had been referred to Prevent because of concerns about his general obsession with violence.

In December 2019, Rudakubana – then aged 13 – returned to the school from which he had been expelled and assaulted a pupil with a hockey stick, breaking their wrist.

In the same year he had told Childline he was going to take a knife into school because of racial bullying.

The NSPCC, which runs Childline, said that one call was “sufficiently serious to breach a threshold which led to Childline informing the local authorities of their concerns”.

Speaking outside court on Monday, Ursula Doyle, the CPS prosecutor, said Rudakubana was “a young man with a sickening and sustained interest in death and violence – he’s shown no signs of remorse”.

Rudakubana is due to be sentenced on Thursday and is expected to be given a life sentence.

However, he cannot be sentenced to a whole-life term for his crimes – which would mean he would not be released from prison except in exceptional compassionate circumstances – because he is under the age of 21.