"In these incidents, their embassy had a presence, some people were arrested. Naturally they will be put on trial, they have made confessions," Ahmad Jannati, the head of Iran's powerful Guardians Council, said at Friday prayers in Tehran.
According to the British government, seven of nine local staff originally detained by the Iranian authorities have now been released.
Iran accused the embassy employees of instigating riots in the unrest that erupted over the disputed re-election of President Mahmoud Ahmadinejad, which was ratified on Monday by the Guardians Council.
Britain has rejected the allegations as baseless and demanded the immediate release of the staff still in detention.
European diplomatic sources said this week that EU nations were considering a proposal from Britain to recall all their ambassadors from Tehran in protest at the Iranian action.
Jannati, who is close to Iran's supreme leader Ayatollah ali Khamenei and a strong Ahmadinejad supporter, said the country's "enemies" had been plotting a "velvet revolution" in the Islamic republic.
Khamenei has described Britain, which has long had turbulent relations with Iran, as the "most evil" of its enemies.
