An attempt to force the Government to demand the return of prisoner Omar Deghayes from Guantanamo Bay has failed.

Three High Court judges have rejected the argument that the former Saltdean student, who has indefinite leave to stay in Britain, should be treated as a UK citizen.

Mr Deghayes, whose brother Abubaker runs the Al Quds mosque in Dyke Road, Brighton, first fled to Brighton with his family when his father was murdered in Libya. He has been held in Guantanamo Bay for more than four years without charge.

Judges admitted he and his fellow detainees "have been subjected at least to inhuman and degrading treatment" at the US detention centre.

His sister Amani said after the ruling yesterday: "This is yet another painful day for us.

"Instead of standing up for my brother, the Government is pretending he's nothing to do with them. It's an illogical and inhumane attitude.

"Omar has been held for more than four years without charge or trial - a complete travesty of justice.

"We've always said that we're not looking for special favours for my brother, just for his fundamental human rights to be respected."

Lord Justice Laws, announcing the Court of Appeal's dismissal, said the refusal to request Mr Deghayes' return did not contravene human rights or race relations laws.

Judges said they could not interfere with the Foreign Office's decision that there was no duty to act because Mr Deghayes and fellow Guantanamo prisoners Bisher Al Rawi and Jamil el-Banna were not British nationals.

Yesterday, campaigners vowed to fight on.

Louise Purbrick, of Save Omar, said: "The story of Pontius Pilate comes to mind - where an execution is about to happen but no one wants to take responsibility for stopping it.

"How are you going to uphold any international law if you don't have a court willing enough to uphold them?

"Instead, Guantanamo Bay seems to be beyond international law. Someone needs to step up and use these laws effectively."

Lord Justice Laws said that a generation ago, the court would have had no jurisdiction over the Government's foreign policies.

He said the reason the courts had moved into this area was the "legal and ethical muscle of human rights and refugee status".

He added: "The prisoners at Guantanamo Bay, some of them at least, have suffered grave deprivations.

"In this appeal we should in our judgment proceed on the premise the detainee claimants have been subjected at least to inhuman and degrading treatment."

But he said there had been no discrimination against the detainees either under human rights or race relations laws and the claim could not be made that the Foreign Secretary failed to treat like cases alike.

Jackie Chase, of Save Omar, said: "We don't need hundreds of pages of legal jargon to tell us what is self-evident: what is going on at Guantanamo is morally abhorrent and our Government's lack of action for Omar and the others is complicity in torture and indefinite detention and is criminal in itself.

"Despite this ruling, the friends, supporters and neighbours of Omar will continue to work for justice for him and for all those held in the United States Gulag that has become a byword for torture."