Downing Street today condemned the continued detention of four Iranians employed by the country's British embassy, as a partial recount of the disputed presidential poll got under way.
Nine embassy staff were arrested on Saturday accused of playing a significant role in the protests. Five have since been released, while the other four are "being interrogated", according Hassan Qashqavi, an Iranian foreign ministry spokesman.
Gordon Brown's spokesman said: "We are deeply concerned at their arrest and their continued detention. These arrests are completely unacceptable and unjustifiable."
Yesterday, the Iranian intelligence minister, Gholam Hossein Mohseini Ejehi, said Tehran had video proof that Iranian employees at the embassy "were distinctly present at the scene of clashes" following the 12 June election.
"The embassy sent its local staff to rallies and inculcated ideas into the protesters and the society," he said.
Speaking last night, the foreign secretary, David Miliband, said some of the nine employees detained had been released.
He denied any had played a role in the clashes between security forces and demonstrators.
"We have protested in strong terms, directly to the Iranian authorities, about the arrests," he said.
"The idea that the British embassy is somehow behind the demonstrations and protests that have been taking place in Tehran ... is wholly without foundation."
The EU demanded that all the detained embassy employees be freed.
The escalation followed attacks on Britain by the Iranian authorities and media, who have singled out the UK for allegedly fomenting trouble. The British embassy is in a compound behind walls three metres high on Ferdowsi Avenue in central Tehran. It has at least 70 local employees.
Harassment by Iranian security forces is common but arrests are not.
Last week, as protests continued over the election, Iran expelled two British diplomats, prompting the tit-for-tat expulsion of two diplomats from Iran's London embassy. The families of British embassy staff have left Iran.
Iran's powerful guardian council began the partial election recount today but has offered to recount only 10% of the votes.
It has dismissed claims of large-scale vote rigging and refused to annul the result, which saw the incumbent president, Mahmoud Ahmadinejad, returned to power.
Ayatollah Ali Khamenei, the supreme leader, denounced "interfering statements" by western officials and appealed to both sides in the dispute "not to stoke the emotions of the young".
But Ali Akbar Rafsanjani, his rival and a former president, demanded a "fair and thorough" review of complaints about the election, in which Ahmadinejad was declared to have won 63% of the vote.
Rafsanjani is backing the reformist candidate Mir Hossein Mousavi, who claims he was the winner.
On his website, Mousavi said he was not dropping his challenge despite pressure from Iran's ruling clergy.
He has rejected a partial recount, and his supporters defied riot police and militiamen to hold a mourning rally outside a mosque in the capital, Tehran.