London, Sept 03: The Iranian ambassador to Britain has returned to Iran amid worsening diplomatic relations between the two countries over the detention in London of a former Iranian diplomat, a foreign office spokesman said today. "We understand that the Iranian ambassador has returned to Tehran but this is not a downgrading of relations," the spokesman told a news agency, without making any further comment.

A diplomatic source in London, quoted by the guardian newspaper, said ambassador Morteza Sarmadi had officially returned for consultations with his superiors following a hastily arranged meeting with British Foreign Secretary Jack straw on Monday. However the source stressed that Sarmadi "may not return" after failing to win any compromise from Straw over the detention last month of former Iranian ambassador to Argentina Hadi Soleimanpur.

Tehran is also angry that straw and the British government have been at the forefront of international demands for Iran to sign an additional protocol to the nuclear non-proliferation treaty that would herald tougher UN inspections of its nuclear facilities.

British pressure over the inspections coupled with the detention of Soleimanpur has led to the diplomatic meltdown. Former ambassador Soleimanpur was arrested in northeast England on an extradition request from Buenos Aires accusing him of taking part in a 1994 bombing of a Jewish centre that killed 85 people.

Bureau Report