Iran has said it will release the eighth of nine British embassy employees detained in Tehran today, Foreign Secretary David Miliband revealed.

Iran has said it will release the eighth of nine British embassy employees detained in Tehran today, Foreign Secretary David Miliband revealed.

But he vowed to continue to fight for the freedom of the remaining detainee who is facing a possible trial on charges Mr Miliband insisted had "absolutely no substance".

The announcement came as another detainee with British citizenship was separately released.

Iason Athanasiadis, a British-Greek journalist had been held for more than two weeks following its disputed presidential election.

Mr Athanasiadis, a freelance reporter who had been working for The Washington Times, was covering the election and its aftermath when he was detained on or around June 19. A dual national with both Greek and British citizenship, he is believed to be the only journalist held in the widespread crackdown who does not hold Iranian citizenship.

Iranian officials have countered that Mousavi's supporters were operating at the behest of foreign powers - namely Britain and the United States.

Officials had also detained nine Iranians working at the British Embassy in Tehran, The staff were arrested last weekend amid rapidly-deteriorating relations with Iran since the disputed re-election of president Mahmoud Ahmadinejad and the street protests that followed.

Mr Milliband said: "I spoke to our ambassador on our daily call last night and the good news is that he was told by the deputy foreign minister that the eighth person would indeed be released today, that the papers have been signed and that there would not be a court process or charges.

"That leaves one more in custody and all of our efforts are now directed towards getting that person out," he told BBC1's Andrew Marr Show.

The embassy's chief political analyst, Hossein Rassam, an Iranian, was identified by his lawyer as the individual who remained in detention facing a charge of "acting against national security".

"The allegations of improper conduct have absolutely no basis," Mr Miliband said, saying the individual was "an honourable, patriotic Iranian, who has been working in a completely open and transparent way for the UK".

"I think it is very, very important that we send a clear message that we are confident about the way he has been doing his job, that we are clear about our goal, which is his release, unharmed and also that there is unity across the international community," he went on.

"It is very important that my anger, my cold anger about the way our staff have been treated, in this case Iranian citizens, doesn't turn into a rhetorical volley at the Iranian regime because that doesn't do anything either for our people or for reform in Iran," he said.

"What's important is that I turn my anger into determination to see that justice is done by our people."

Mr Miliband accused the regime of a "grim and gruesome" clampdown and said no government should "abuse the rights" of its citizens.

"There has been a grim and gruesome clampdown - more than 20 people have lost their lives, at least on the reported level," he said.

"The history of the last 20 or 30 years not just in Iran but elsewhere is that repression can work in the short term but legitimacy counts."

Diplomatic tensions are running extremely high between the two countries, with the Iranian authorities seeking to blame Britain for stirring anti-government unrest.

Britain has criticised Iran's crackdown on protesters and there have already been tit-for-tat expulsions of diplomats.

Iran's Ambassador to London, Rasoul Movahedian, was summoned by the Foreign Office on Friday as part of a coordinated action across European Union countries.

Asked if he believed the election had been fair, the Foreign Secretary said: "What I know is that many people in Iran think it is very odd indeed that in a large number of cities, the number of votes allegedly cast is greater than the number of voters.

"We have always said that it is for the Iranian people to decide their government but it is for their government to protect their people, not abuse their rights."