Richard Dawkins and Christopher Hitchens - who have both written books promoting atheism - have asked human rights lawyers to produce a case for charging Pope Benedict XVI over his alleged cover-up of sexual abuse in the Catholic church.
The pair believe they can exploit the same legal principle used to arrest Augusto Pinochet, the late Chilean dictator, when he visited Britain in 1998.
Dawkins and Hitchens believe the Pope would be unable to claim diplomatic immunity from arrest because, although his tour is categorised as a state visit, he is not the head of a state recognised by the United Nations.
They have commissioned the barrister Geoffrey Robertson and Mark Stephens, a solicitor, to present a justification for legal action.
The lawyers believe they can ask the Crown Prosecution Service to initiate criminal proceedings against the Pope, launch their own civil action against him or refer his case to the International Criminal Court.