He criticised the Afghan authorities, saying that liberated countries needed to respect democratic rights. “I am deeply troubled when I hear that a person who may have converted away from Islam may be held accountable,” Mr Bush said.

His comments came after the arrest of Abdul Rahman this month. Under the 2004 Afghan Constitution, Mr Rahman could face the death penalty for an attack on Islam.

But yesterday it appeared that the case could be dismissed on a technicality if Mr Rahman were found mentally unfit to stand trial.

A relative described the defendant as “silly and like a child”. “I am scared because he is my brother and he is not 100 per cent healthy — he has psychological problems.”

Britain, Italy and Germany have also spoken out against the Western-backed Government of President Karzai for its failure to stop the prosecution of Mr Rahman.

Kim Howells, Foreign and Commonwealth Office minister, said that he was seeking “urgent clarification” about the case from Afghanistan, where about 5,000 British troops will be deployed this summer.

“Individuals should be able to practise their faith free from persecution. We take every opportunity to urge states to implement laws and practices which foster tolerance and mutual respect,” he said.

Gianfranco Fini, the Italian Foreign Minister, summoned the Afghan Ambassador to “shed light” on the case and told the Italian envoy to Kabul to make urgent representations to the Afghan authorities.

Frank-Walter Steinmeier, the German Foreign Minister, said that he viewed the case with “great concern”.

In Kabul the authorities appeared surprised by the outcry but insisted that the judicial process had to be respected.

But a human rights expert in the city said that the defendant’s mental state could provide the authorities with an excuse to drop the case, but warned that “something like this will come up again”.

“They don’t want to upset their big donors, but this case highlights the gulf between Sharia law and statutory law.”

Explore World News

• Iraq News

• US & Americas News

• Europe News

• Middle East News

• Asia News

• Africa News

• Ireland News

Times Recommends

• The truth behind Obama's meteoric ascent
• Christians flee Iraq amid religious cleansing
• Aid agencies: 5m face starvation in Zimbabwe