Axel Rudakubana, 18, admitted killing the girls and stabbing 10 others last July in the northern English town of Southport, an atrocity that shocked Britain and was followed by nationwide rioting. He was sentenced to at least 52 years behind bars last month.

Judge Julian Goose said he could not impose a full life sentence as Rudakubana was 17 when the attack took place but he was unlikely ever to be released.

Hermer said in a statement late on Friday that his office had received multiple requests to review the sentence under the unduly lenient sentence scheme, designed to identify and remedy gross errors made by judges.

“After careful consideration of independent legal advice and consultation with leading criminal barristers and the crown prosecution service, I have concluded that this case cannot properly be referred to the court of appeal,” Hermer said.

The attorney general said Rudakubana’s sentence was the second longest sentence imposed by the courts in English history, and that he was likely to spend the rest of his life in jail.

“No one would want the families to be put through an unnecessary further court process where there is no realistic legal basis for an increased sentence,” Harmer said.

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