A UK resident held at Guantánamo in Cuba may be losing his mind in solitary confinement even as the British government is negotiating his release, according to lawyers and British members of parliament.

The case of Iraqi-born Bisher al-Rawi, seized by the Central Intelligence Agency four years ago and first sent to a secret prison in Afghanistan, highlights the complications facing the Bush administration as it tries to empty Guantánamo and draw a line under what officials admit were excesses in the wake of the September 2001 attacks by al-Qaeda.