TER ROR suspect David Hicks isn't confident his British citizenship will secure his release from detention at Guantanamo Bay, his father said today. The British Government said today it would appeal a British High Court ruling two weeks ago in which a judge ruled there was "no power in law" to deprive Adelaide-born Hicks of British citizenship.

Hicks, whose mother is British, has been detained by the US since his capture among Taliban forces in Afghanistan in December 2001.

Britain's Home Office said today it would appeal the High Court ruling which granted British citizenship to Hicks, a 30-year-old Muslim convert from Adelaide.

"The ruling by the courts was a disappointment. The Home Office was granted permission to make an appeal and we have done so," a Home Office spokesman said. No date has been set for the appeal.

Hicks' legal team hoped the granting of a British passport would force the UK to release him from Guantanamo Bay because Britain refuses to allow its citizens to be tried before US military commissions, saying they do not meet international standards of law.

Hicks last year pleaded not guilty to charges of conspiracy, attempted murder and aiding the enemy at a commission hearing but it remains unknown when he will face trial.

His father, Terry Hicks, spoke to his son by telephone on Christmas Eve.

"He wasn't 100 per cent, he was pretty down," Terry Hicks said today.

"I think he's more or less playing it by ear, the mode he's in is 'whatever happens, happens'.

"He's aware that he's a British citizen, for a little while at least, but he's not overly confident of getting released because of it."

Mr Hicks said the British Government's appeal was expected, but would delay his son's bid for freedom.

"The High Court was water-tight, this is just (a) delaying tactic from their end," Mr Hicks said.

He said his son had been transferred to a section of the US military detention facility at Guantanamo Bay known as Camp Delta.

Hicks, who was suffering from back and eyesight problems, was in the area with one other detainee who didn't speak English and was forbidden from speaking to guards.

"I think it's just bloody disgusting what they're doing to him," Mr Hicks said.