Britain has refused to repatriate UK residents held at Guantanamo Bay because the US terms of release were too stiff, the lord chancellor says.
Guantanamo Bay has angered human rights groups
Lord Falconer confirmed that there was "continuing dialogue" with the US over the Cuba detainees.
But he added: "We could not take people back into the UK on terms that we could not legally deliver."
At least nine UK residents are thought to remain among the detainees and nine Britons have already been released.
Earlier, the Guardian newspaper claimed to have seen leaked documents revealing how the Americans had demanded that any freed detainees would be stopped from leaving the UK.
US officials, the newspaper said, also wanted to be sure that the British would know immediately if the freed men met known extremists, or planned, supported or promoted extremism or violence.
The lord chancellor has previously described Guantanamo Bay as a "shocking affront to the principles of democracy".
He used a speech to an American university on Tuesday to renew his attack.
He told the Georgetown University Law Centre that terrorists needed to be starved of "perceived legitimacy".
"Every time we fail to stand by our values we run the risk of acting as recruiting sergeants for terrorism," he said.
Nine British citizens have been released from the Cuba camp in the past two years.
All were questioned by UK police on their return, but none was charged with any offence.