A notorious murderer who has served 40 years for killing three police officers has lost his case for parole.

Harry Roberts was jailed in 1966 for murdering three plain-clothes and unarmed officers, PC Geoffrey Fox, 41, Sgt Christopher Head, 30, and Det Con David Wombwell, 25.

The men were shot dead in Shepherd's Bush, West London, after they pulled over a van containing Roberts and his accomplices, John Duddy and John Witney, after an armed robbery.

The 70-year-old, one of Britain's longest-serving prisoners, is an inmate at a low-security prison near Newton Abbot, Devon, and could take his case to the European Court of Human Rights. Roberts' 30-year tariff expired nine years ago, but calls to release him have been rejected. In July last year, he lost an appeal to the House of Lords over the use of secret evidence.

One of Sgt Head's surviving sisters, Edna Palmer, 83, from Gillingham, Kent, said she "felt better" knowing he is being kept behind bars. She said: "I do not think anyone should be let out of jail if they have killed someone."

A spokesman for the Parole Board said: "With all life-sentence prisoners, the statutory test is whether it is necessary for the protection of the public that the prisoner be detained."

A "let Harry out for Christmas" campaign was staged by Roberts' supporters, who held a candlelight vigil outside Peckham Police Station in south-east London. A spokesman for the group, Dan Thurwen has said: "We know that it was wrong what Harry did, but he has served his time and now he deserves a chance to go free."