Britain's beleaguered Prime Minister Theresa May has been urged to sack her Foreign Secretary Boris Johnson over his handling of the Nazanin Zaghari-Ratcliffe case.

On Sunday both Labour leader Jeremy Corbyn and London Mayor Sadiq Khan called on May to fire Johnson -- who has been under increasing pressure since Iranian state TV claimed that his statements on the plight of the British-Iranian woman imprisoned in Tehran on charges of espionage confirmed her guilt.