An eighth British embassy worker in Tehran is due to be released, leaving one remaining in custody.
UK Foreign Secretary David Miliband said the international community is united in its opposition to intimidation from Tehran, which claimed embassy staff had been active in supporting opposition protests after the recent election.
Meanwhile, defeated Iranian presidential candidate Mir-Hossein Mousavi has released a new 25-page report detailing fraud and irregularities in last month's vote.
The report accuses President Mahmoud Ahmadinejad of abusing the state machinery during the campaign.
It says the incumbent had distributed cash to secure the votes of working class Iranians.
The report accuses the interior ministry, which was charged with organising the election, and the Guardians Council, the official electoral supervisory body, of being biased towards Mr Ahmadinejad.
It says members of the council had publicly supported the incumbent before and during the campaign.
The report asks why the interior ministry had printed 14m more ballots than the total registered electorate of some 46m.
