Hossein Moussavian was the spokesman of the moderate nuclear negotiating team that served under president Mohammad Khatami and was replaced when hardliner Ahmadinejad became president in 2005.

"In the investigation it was concluded that he committed no crime and a decision was taken not to continue the investigation," the source in the Iranian judiciary told AFP, asking not to be named.

"This means that there is no accusation against him," the source added.

The judiciary announcement comes after Ahmadinejad and other government members publicly accused Moussavian of being a criminal who had passed on secrets about Iran's nuclear programme.

Intelligence Minister Gholam Hossein Mohseni Ejeie had even said the allegations against him were "proven" and that Moussavian had passed classified information to the British embassy in Tehran.

Government spokesman Gholam Hossein Elham on Tuesday again made no secret of the government's desire to see Moussavian in the dock, however.

"Everything that has been said, notably by the intelligence minister, is accusations. Only a judge can condemn him in a public trial," he told reporters.

"We hope that with a public trial the affair will be cleared up."

Moussavian is a close ally of Ahmadinejad's rival, former president Akbar Hashemi Rafsanjani. He was detained briefly in May but was released on bail.

His case then disappeared from view for several months until Ahmadinejad accused his critics of "pressuring the judge to acquit a spy" in a security case.

Ahmadinejad did not mention Moussavian by name, but observers saw the remarks as an unmistakable reference to the former nuclear official.

Moussavian, also a former ambassador to Germany, is now the deputy head of a research institute led by Hassan Rowhani, who was Iran's top nuclear negotiator at the time and has since been bitterly critical of Ahmadinejad.

The research institute is run by the Expediency Council, Iran's top political arbitration body headed by Rafsanjani, who was soundly defeated by Ahmadinejad in the 2005 presidential election.

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