Mr Mohamed, a British resident, claims he was tortured in US custody
Lawyers for a UK resident freed from Guantanamo Bay have urged two High Court judges to reopen a judgement not to disclose all evidence in his case.
The judges had refused to publish paragraphs summarising US government reports on Binyam Mohamed's treatment, central to his claims of torture.
This was based on fears disclosure might compromise the UK's intelligence-sharing relationship with the US.
But his lawyers have since said these fears were not correct.
Mr Mohamed claims he was subjected to torture and cruel, inhuman or degrading treatment with the consent of UK authorities.
During the High Court hearing in 2008, lawyers for Foreign Secretary David Miliband said the US government remained opposed to publication of the seven paragraphs outlining his treatment, even under the new Obama administration.
But Mr Mohamed's lawyer, Dinah Rose QC, told Lord Justice Thomas and Mr Justice Lloyd Jones it had since become clear from statements made by Mr Miliband and others that this was not correct.
She said the supposed threat from the US to withdraw intelligence co-operation was not based on any contact with the Obama government.
Nor was it based on any knowledge as to whether or not his administration would maintain the position adopted under President George W Bush, and in fact, there was no such threat.
Ms Rose said it was "regrettable" the foreign secretary did not correct the error at the time of the court's judgment.
The true position of the new US administration remained "opaque," she said.
Considerable care had been taken by the US government and by Foreign Office lawyers in "carefully crafted and ambiguous statements" - to avoid saying whether the US would reconsider its intelligence-sharing relationship with the UK if the material were placed in the public domain.
Ms Rose said: "The court should expect to see clear evidence before concluding that the US Government would act in such an extraordinary manner in response to the judgment of an independent court of its leading ally in a matter of overwhelming public interest and in circumstances in which, as the court has found, publication would not raise any national security issue."
Ethiopian-born Binyam Mohamed, 30, alleges he was tortured into falsely confessing to terrorist activities before he arrived at the Guantanamo Bay. The US denies the claims.
The last UK resident in the facility, Mr Mohamed returned to the UK in February.