A triple killer was given an “unduly lenient” sentence because European rules deem life sentences as “inhumane”, a court heard.

Ian McLoughlin was given a 40-year sentence after stabbing a man to death while on day release from prison.

But Attorney-General Dominic Grieve believes McLoughlin should have been imprisoned for life and has referred his case to appeal judges.

The 55-year-old was imprisoned in October for stabbing a man while on his first day release after serving 21 years for the brutal murder of a Brighton barman in 1992.

Justice Sweeney imposed a 40-year tariff at the Old Bailey and added he could not pass a whole-life term because of a European ruling.

Last year the European Court of Human Rights deemed whole-life terms “inhuman and degrading treatment” and criminals should be entitled to a review of their sentence 25 years into their term at the latest.

McLoughlin stabbed 66-year-old Graham Buck as he came to the aid of a neighbour in Little Gaddesden in Hertfordshire last July.

He was on day release from his minimum term 25-year sentence for the brutal murder of 56-year-old barman Peter Halls in Brighton in September 1990.

Mr Halls, who ran The Volks Tavern in Madeira Drive, The Eastern in East- ern Road, and the American Bar of the Norfolk Resort Hotel in King’s Road, was found dead in his flat in Sillwood Road, Brighton, after being stabbed three times in the neck.

McLoughlin, who had been offered work at one of Mr Halls’ pubs, said he assumed the bar owner was gay and thought that he might be expected to sleep with him.

He was also jailed for eight years for the manslaughter of a man in North London after beating him to death with a hammer and stashing his body in a cupboard in 1984.

Judges at the Court of Appeal heard McLoughlin did not want any argument to be made on his behalf to avoid upsetting Mr Buck’s family.

It was argued on behalf of the Attorney-General that the “failure to impose a whole-life order renders the sentence unduly lenient”.

Speaking after the hearing, Mr Grieve said: “This hearing was about preserving the principle that whole-life orders can be imposed for particularly heinous and serious crimes.

“I asked the Court of Appeal to look again at the sentence handed down to Ian McLoughlin as I believed the sentencing judge mistakenly took into account a decision of the European Court of Human Rights which is inconsistent with the domestic legislation and case law by which he was bound.

“I believed the seriousness of this case required a whole-life order because McLoughlin had a previous conviction for manslaughter in 1984, a conviction for murder in 1992, and because the murder for which he was being sentenced was committed in the course of robbery.”

Appeal judges yesterday reserved their decision to consider the matters and promised to return a verdict as soon as possible.