The brother of Guantanamo Bay inmate Omar Deghayes has rubbished US claims that he and four other detainees the British Government wants released could commit terrorist atrocities in the UK.

The Foreign Office formally asked for Mr Deghayes and the other four British residents to be returned to the UK in a policy U-turn last week.

Supporters of the Save Omar campaign celebrated the prospect of his swift return.

But the US government was reported in The Sunday Times as warning the five could take part in terror attacks in the future.

A Pentagon official was quoted as saying: "Among these men are some extremely dangerous individuals, if they are sent back to the United Kingdom they could pose a risk.

"Because of some of the extensive ties these individuals have with well-known Al-Qaeda leaders, we have concerns that they will try to reconnect with some of their old counterparts and return to the fight in the sense that they will try to carry out attacks, whether it's in England or elsewhere."

Mr Deghayes, 37, was described as a "jihadi veteran" who has "direct connections to Al-Qaeda operatives in Europe.

The Pentagon reportedly suspects him of being involved in the Bosnian war as a fundamentalist Muslim, with links to a suicide bombing in Casablanca.

He has previously been accused of taking part in the civil war in Chechnya.

Mr Deghayes's brother, Abubaker, told The Argus: "It is typical they would say that.

"They have had him for five years under constant interrogation, and they haven't come up with any evidence that he has anything to do with Al-Qaeda.

"If they're not going to charge him they should let him go."

Clive Stafford Smith, who is the five men's lawyer, said the US claim was "a blatant attempt to smear my clients".

Omar was arrested in Pakistan in 2001 after reportedly travelling to the region to do voluntary work.

He has been held without charge at Camp Delta in Guantanamo Bay since 2002.

By January 2005 the Government had secured the release and return of all UK nationals detained at the centre but had not sought the release of this group of men.

The Argus launched its Justice For Omar campaign to press the US government to either charge Omar or send him home.

Labour MPs Des Turner, of Brighton Kemptown, and Celia Barlow, of Hove and Portslade, welcomed the Government's decision to request the return of Mr Deghayes and the other inmates this week.

But Shadow Home Secretary David Davis said the US Government's warning should prompt ministers to decide whether any further measures such as control orders will be used against the five when they return.

He said: "Given clear concerns of a potential threat to both Britain and our allies it is incumbent upon the Home Secretary to explain precisely how she is going to protect the safety of our citizens.

"Does she propose to grant leave to remain? Does she propose to put them under ineffective control orders? What precisely does the Government intend to do now they have been granted their wish for the release of these people?"

None of the five men the Government has asked to be returned are British nationals but all were legally resident in the UK when they were detained.

Mr Deghayes moved to Brighton in 1986 after his family fled Libya. They believed his father had been killed by Colonel Gaddafi's government.

The other men are Shaker Aamer, a London resident originally from Saudi Arabia, Jamil El Banna, a Jordanian refugee whose family lives in Dollis Hill, North-West London, Binyam Mohamed, who lived in Kensington, West London, and had applied for asylum from Ethiopia, and Abdennour Sameur, a refugee from Algeria who lived in Bournemouth.