'The situation for them is unbearable and they are under surveillance,' said Merz. The men are in the Swiss embassy in Tripoli awaiting permission to leave Libya.

Two weeks ago Merz travelled to Triploi to sign an accord and to apologize for the arrest of the son of Libyan leader Moammar Gaddafi. Hannibal Gaddafi and his wife were accused of mistreating their domestic staff during a stay in Geneva.

Merz was given assurances by the Libyan prime minister, al-Baghdadi Ali al-Mahmoudi, that the Swiss businessmen would be allowed to return home by Sep 1. However, to date they have still not received the necessary permission to leave.

Under the accord, both Switzerland and Libya were to appoint their arbitrators for an international tribunal which is due to examine the circumstances surrounding Hannibal's arrest.