A lawyer for three Britons held at Guantanamo Bay has accused the British and US governments of releasing only those whose cases threatened to create bad publicity.
The detainees have been held at the camp for two years without trial
Gareth Peirce represents two detainees who are to be freed from the army base in Cuba, as well as Moazzam Begg, 36, one of the four who must stay.
Ms Peirce told BBC Radio 4's Today programme politicians had chosen to send home detainees whose cases had reached the US Supreme Court, where a defeat could be damaging for President George Bush.
She said: "We have a real concern that a deal has been struck.
"The return of a number, of whom I represent two, is very convenient in order to leave others behind who are creating less pressure.
DETAINEES BEING RELEASED
Shafiq Rasul, 24, of Tipton, West Midlands
Asif Iqbal, 20, of Tipton
Ruhal Ahmed, 21, of Tipton
Jamal Udeen, 35, from Manchester
Tarek Dergoul, 24, from east London
"Two of those who are coming back are the two who have succeeded in getting to the door of the Supreme Court in the US to bring a challenge which, if it was found against the Bush government, would be highly inconvenient in an election year.
"Those who are not coming back include Moazzam Begg, and there is a deep concern that there has been a trade-off between the two governments."
On Friday, a Pentagon source told the BBC the five British detainees may not be told of their release until just before they are to be freed, which could be weeks away.
Major General Geoffrey Miller, the commander of the US base in Cuba, said all five were terrorist suspects or were suspected of supporting terrorism.
BRITISH MEN STILL BEING HELD
Moazzam Begg, 36, from Birmingham
Feroz Abbasi, 23, from south London
Martin Mubanga, 29, from north London
Richard Belmar, 23, from London
The officer said they were now seen as "low risk", and the UK government had said it did not regard them as a threat to national security.
Nine Britons have been among about 650 terror suspects held at the United States base on Cuba for two years without trial.
Most are believed to have been arrested in Pakistan or Afghanistan as suspected al-Qaeda or Taleban fighters.
Peter Clarke, head of anti-terrorism at Scotland Yard, said the police had a responsibility to investigate circumstances that had led to the suspects' detention.
'Case for treason'
The five men being released are: Shafiq Rasul, of Tipton, West Midlands; Asif Iqbal, of Tipton; Ruhal Ahmed, of Tipton; Jamal Udeen, from Manchester, and Tarek Dergoul, from east London.
They do not include Feroz Abbasi or Mr Begg, who face potential trials before a military tribunal in the US, according to the authorities there.
Shadow home secretary David Davis said: "If they fought against coalition troops on the battlefield, they should also be charged and tried in the UK.
"In addition, I think there may be a case for treason."