The refusal by the Government to request the return of three British residents held in the US detention centre at Guantanamo Bay is unlawful, the Court of Appeal was told.

Rabinder Singh QC, acting for the families of the men, who had indefinite leave to stay in Britain, said they should be treated as UK citizens although they are foreign nationals.

There was "credible evidence" that Omar Deghayes, from Saltdean, Bisher Al Rawi, from Kingston upon Thames, and Jamil el-Banna, from Willesden, had suffered torture at the hands of US interrogators.

Two senior High Court judges refused to quash the decision not to demand their release after a hearing in May this year.

They had been asked to declare that the men, although foreign nationals, were long-term UK residents who were entitled to help similar to that received by British citizens who were freed from Guantanamo in March 2004 and January 2005 after Foreign Office requests for their release.

But the judges said they could not interfere with a Foreign Office decision that there was no duty to act because the men were not British nationals.

Mr Rabinder Singh said yesterday the Government's continuing refusal to act was contrary to the Race Relations Act and was breaching the rights of the mens' families, who are British citizens.

He said the Government's main argument for refusal - that because the three were not British citizens the UK cannot provide them with consular protection or support - had now "fallen away".

The US had indicated it would not reject a request for release because of their nationality and the sole obstacle was over security arrangements which the UK would have to put in place after release, said the QC.

He said:"None of the detainee claimants have any meaningful ties to any other country and Mr el-Banna and Mr Deghayes, as refugees, have been accepted by the UK as at risk of persecution or torture were they returned to their countries of nationality."

Mr Rabinder Singh said each man had been subjected to arbitrary detention without trial - Mr Al Rawi and Mr el-Banna for three years and eight months and four years and three months for Mr Deghayes.

The hearing, expected to last three days, was adjourned until today.