But the court held that the particular facts of the case, "horrifying though they were", did not justify a "life means life" sentence.

The former US marine, convicted four years ago of murdering PC Broadhurst in December 2003, was told he will now serve a minimum term of 37 years before being considered for release on licence.

On Wednesday, three judges rejected argument by defence lawyers that whole-life jail terms in principle amounted to a breach of Article 3 of the European Convention on Human Rights, which states that no-one shall be subjected to "inhuman or degrading treatment or punishment".

Bieber, 42, was found guilty by a jury at Newcastle Crown Court in 2004 of the murder of PC Broadhurst .

The 34-year-old was shot at point-blank range during a routine check on a stolen vehicle in Gipton.

Bieber was also convicted of the attempted murders of PC Broadhurst's colleagues, PCs Neil Roper and James Banks.

He became one of only 25 people at the time to have been given a whole-life sentence in England and Wales.

Bieber had claimed a friend, a fellow US national from Florida, was the gunman, but refused to name him.

In October 2006, the Court of Appeal rejected Bieber's appeal against his convictions, saying the evidence against him was "overwhelming".

Lord Phillips, sitting with Mr Justice Pitchford and Mrs Justice Dobbs, said Bieber's lawyers had argued that an irreducible life sentence, with no prospect of release and regardless of any progress made by the prisoner towards rehabilitation, amounted to inhuman treatment.

But the judge said the European Court of Human Rights in Strasbourg had so far not held that an irreducible life sentence breached Article 3, although its approach to the issue might change in future.

In any event, a whole life term should not be regarded as irreducible because the Home Secretary had the power to order a prisoner's release on compassionate grounds - for instance, when an inmate was terminally ill or incapacitated.

This power was used sparingly, but if the stage was reached where continued imprisonment was held to be inhuman or degrading, "we can see no reason why the Secretary of State should not use that power to release the prisoner".