The four Britons sent home from Guantanamo Bay on Tuesday and set free from police custody last night still pose a terrorist threat, the United States said.

Lieutenant Commander Flex Plexico, a Pentagon spokesman, said: "We continue to believe that these individuals pose a significant threat. British authorities have assured us that they will take the necessary steps to address the threat posed by these individuals."

The four former detainees are today enjoying their first day of freedom in more than three years after being spirited out of Paddington Green police station last night. They had been questioned there following their return to Britain.

The men were escorted to a location of their choice to be reunited with their families, evading the waiting media.

Louise Christian, the civil liberties lawyer representing Mr Mubanga and Mr Abbasi, said that all four were driven to separate locations, where they were expected to be reunited with their families. "They want to be reunited with their family members in private," she said.

Azmat Begg, father of Moazzam Begg , rejected US claims that his son was still a risk to security. He said nothing had been proved against his son. "I have heard from my son that they have taken more than 300 interviews. Everything has been done and nothing has been proved. No evidence is there of anything."

Asked if Moazzam was bitter or angry, Mr Begg said: "No, he is very quiet, he is very determined. He wants to fight for people who are still there and he is definite and sure that they are not terrorists."

Moazzam Begg, 36, from Birmingham, Mr Abbasi, 25, from Croydon, South London, Mr Mubanga, 32, from Wembley, West London, and Mr Belmar, 25, from St John’s Wood, North London, had spent three years in American custody at the Cuban base, accused of links with al-Qaeda.

Asked about the Americans' warning, Charles Clarke, the Home Secretary, told BBC Radio 4's Today programme: "It is a matter I have to constantly review. I believe we have carried out due process with those individuals."

He said Britain had listened to the US's concerns: "Every practical step is being taken by the relevant authorities to maintain national security."

Mr Clarke insisted his new proposals to hold terror suspects under indefinite house arrest, announced yesterday, were not part of a deal with the US to secure the Guantanamo detainees' release. "I can give an absolute assurance that isn't the case. I have not discussed these measures with the Americans."

The Home Secretary was non-committal when asked whether Moazzam Begg, Martin Mubanga, Feroz Abbasi and Richard Belmar would now be subject to the new powers if they were already on the statute book.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Time-worn Freddie gives up Test matches
• Brighton company 'involved in cyber attack'
• The art of survival: it's all in the mind