Gordon Brown stepped up the pressure on Iran to free the British Embassy employees seized in Tehran by declaring their arrests “unacceptable, unjustified and without foundation” and hinting at concerted international action.

One option being considered by the European Union’s member states is for all 27 to withdraw their ambassadors from Tehran temporarily as a collective protest, a European diplomat told The Times.

The idea was discussed by EU foreign ministers who met in Corfu on Sunday and later promised “strong and collective action” if the four employees still being held were not freed quickly. The EU is one of Iran’s biggest trading partners.

Hillary Clinton, the US Secretary of State, also decried Iran’s “deplorable” treatment of the employees. Silvio Berlusconi, the Italian Prime Minister, hinted that the G8 summit he will host next week could adopt sanctions against Iran.

Undeterred, the regime yesterday staged a partial recount of the presidential election votes which, to no one’s surprise, confirmed the re-election of President Ahmadinejad.

Mr Ahmadinejad also announced an investigation into the death of Neda Soltan, the young student who was shot dead during a demonstration in Tehran and became a global symbol of the regime’s brutality. Opponents said that the investigation, like the recount, was a charade intended to counter international criticism.

Indeed Mr Ahmadinejad appeared to prejudge the outcome by telling Ayatollah Mahmoud Hashemi Shahroudi, the head of the judiciary: “Given the many fabricated reports around this heartbreaking incident and the widespread propaganda by the foreign media . . . it seems there is clear interference by the enemies of Iran who want to misuse the situation politically and tarnish the clean image of the Islamic republic. Therefore I am asking you to order the judicial authorities to probe the killing of this woman with utmost seriousness and identify and prosecute the elements behind the killing.”

Miss Soltan, 26, was widely reported to have been shot by a Basij — an Islamic volunteer militiaman. A doctor who was standing beside her told The Times last week that she was killed by a Basij on a motorbike who was immediately caught by the crowd and confessed. The regime, however, has variously blamed her killing on fellow demonstrators, the BBC’s Tehran correspondent Jon Leyne, the CIA and agents of Iran's foreign enemies.

Hossein Taeb, Iran’s Basij commander, claimed yesterday that armed imposters had dressed up as Basiji and caused mayhem at rallies to give his men a bad name. “Basij forces are not authorised to carry weapons,” he said.

Azizallah Rajabzadeh, Tehran’s police chief, likewise insisted that his men were not authorised to use firearms.

The regime has freed five of the nine Iranian employees of the British Embassy that it accused on Sunday of fomenting unrest, but it still holds four and Gholam Hossein Mohseini Ejehi, the Intelligence Minister, yesterday claimed to have videotape showing them mixing with demonstrators. The courts would decide their fate, he said.

On Sunday night David Miliband, the Foreign Secretary, called Manouchehr Mottaki, Iran’s Foreign Minister, to insist that the charges were baseless. Yesterday Mr Brown reinforced that message. He said: “Iran’s actions, first the expulsion of two diplomats, and now the arrest of a number of our locally engaged staff, is unacceptable, unjustified and without foundation, and we, with our international partners, will continue to make this clear to the Iranian regime”.

He was speaking at a joint appearance with José Manuel Barroso, president of the European Commission, who expressed “full solidarity” with Britain and declared that “intimidation and harassment are unacceptable”.

The four have not been named but are believed to work in the embassy’s political section. Sources said that the Government was considering various options if they were not freed but would not discuss them because it was trying to prevent the confrontation from spiralling out of control.

There was some evidence that the regime was also trying to defuse the row. Hassan Qashqavi, the Foreign Ministry spokesman, said that “reduction of diplomatic ties is not on our agenda”, contradicting other Iranian officials who said last week that the regime was considering downgrading relations with Britain.

Additional security forces were deployed on the streets of Tehran last night as the results of the recount of 10 per cent of the presidential vote were announced. The Guardian Council confirmed Mr Ahmadinejad’s victory, but that came as no surprise because Ayatollah Ali Khamenei, the Supreme Leader, and other leading officials in the regime had already declared unequivocally that he was the winner and rejected charges of vote-rigging.

Mir Hossein Mousavi and Mehdi Karroubi, two of the defeated candidates, had dismissed the recount as meaningless and reiterated their demand for a fresh election.

They said that the recount would take no account of ballot-box stuffing or a host of other breaches of electoral law.

Decades of discord

1951 Iran nationalises precursor of BP, the Anglo-Iranian Oil Company, triggering a dispute with Britain

1953 The Prime Minister, Mohammed Mossadeq, deposed in a coup with British and US backing

1980 Britain closes its embassy in Tehran after the Islamic revolution

1989 The Iranian leader Ayatollah Khomeini calls on Muslims to kill the British author Salman Rushdie for blasphemy in The Satanic Verses; breaks ties with Britain

1994 Britain accuses Iran of having secret contacts with the IRA

1999 Relations are upgraded after Iran dissociates itself from Rushdie death sentence

2007 Iran seizes eight Royal Navy sailors and seven Marines in Shatt al-Arab waterway that separates Iran and Iraq; freed after 12 days

June 18, 2009 Britain freezes $1.6 billion under international sanctions over Tehran’s nuclear programme

June 19 In post-election unrest, Ayatollah Ali Khamenei, Supreme Leader, calls Britain “the most treacherous” of enemies

June 23 Britain expels two Iranian diplomats after Iran forces out two British diplomats

Sources: Reuters; Times archive

Times Recommends

• African migrants desperate for a better life
• Karzai, the Anglophile who alienated the West
• They killed my family, but I rise again