A high-ranking Iranian cleric said Friday that Iran planned to put some of the detained British Embassy staff members on trial, a move that could provoke a tightening of European sanctions against Iran, including the withdrawal of ambassadors. The cleric, Ayatollah Ahmad Jannati, the head of the influential Guardian Council, told worshippers at Friday prayer in Tehran that the embassy employees had 'made confessions' and would be tried for their role in inciting protests after last month's disputed presidential election. In London, the Foreign Office said it was urgently seeking clarification from the Iranian government as to whether the cleric's remarks represented official policy. 'We are confident that our staff have not engaged in any improper or illegal behavior,' Foreign Secretary David Miliband said in a statement. 'We remain deeply concerned about the two members of our staff who remain in detention in Iran.' He said he planned to speak to the Iranian foreign minister, Manouchehr Mottaki. Of the nine staff members seized Sunday, five were released Monday after the first British and European protests, and Iranian state media said Wednesday that three more had been freed, leaving only one in custody. British officials, however, said that two remained under arrest. As local employees of the embassy, those arrested did not have diplomatic immunity. None are British citizens. Although the Foreign Office has denied that it had any role in stirring the ferment in Iran, officials in London have said that the embassy in Tehran had not forbidden its local employees from participating in the protests as individuals. The Iranian authorities say they have video of some embassy employees at the protests. Hours after the threat of trials, the European Union seemed to hold back from an out-and-out showdown, resolving to summon Iranian ambassadors in all 27 of the group's countries to send 'a strong message of protest against the detention of British Embassy local staff and to demand their immediate release,' said a European diplomat who spoke on condition of anonymity, following the group's rules. Other graduated measures -- like a slowdown in issuing visas to Iranian officials seeking to visit Europe and a potential withdrawal of all European ambassadors -- would be considered, the diplomat said. He said Iranian diplomats would be told that the arrest of the embassy employees and the threat of trials were considered a threat to all European Union diplomatic staff members in Iran. The Iranian authorities accused the employees of fomenting and orchestrating the protests that drew tens of thousands of Iranians into Tehran's streets after the June 12 election. The demonstrations provoked a security crackdown that had largely ended the public protests but not the political ferment over the elections. The hard-line incumbent president, Mahmoud Ahmadinejad, has been officially declared the winner by a landslide, but his main opponent, Mir Hussein Moussavi, has vowed to continue his campaign to have the official result declared fraudulent. Jannati, who is an ally of Iran's supreme leader, Ayatollah Ali Khamenei, did not say how many of the detainees would be tried or on what charges, news reports said. But, in unofficial translations provided by news agencies, he said that the British Embassy had a 'presence' in the postelection unrest and that 'some people' had been arrested. It was 'inevitable' that they would face trial, he said. The Guardian Council is an influential panel of 12 clerics whose responsibilities include vetting elections. On Monday it certified Ahmadinejad's victory, a step that emboldened hard-line officials to warn of a harsher crackdown if protests continued. Britain has sought diplomatic help from the European Union, which is thought to hold more sway with Iran. But some European countries, led by Germany, have been reluctant to risk worsening ties with Iran, particularly at a time when European diplomats have been pressing it for concessions over its nuclear program. They have argued that a withdrawal of envoys, a step urged by Britain, would leave few diplomatic options if the crisis deteriorated further. But there were signs that the threat of trials had stiffened resolve in other countries. 'Our solidarity with Britain is total,' said President Nicolas Sarkozy of France, adding that France favored tightening sanctions. The Iranian authorities have frequently blamed foreigners for the turmoil, but they have singled out the British as instigators. They cited Britain's covert role in past political upheavals, including the toppling in 1941 of Reza Shah Pahlavi, suspected of having pro-German sympathies during World War II, and the ouster in 1953 of Prime Minister Mohammed Mossadegh after his government nationalized Iran's British-dominated oil industry. At the same time, Tehran has sent mixed signals about the fate of the embassy employees. Hassan Qashqavi, the foreign ministry spokesman, said Monday that Iran was eager to maintain normal diplomatic relations with the European Union, its biggest trading partner. 'Reduction of ties is not on our agenda with any European country, including Britain,' he said. But on Wednesday, the semiofficial Fars news agency said that one of the embassy employees, who was not identified by name, 'had a remarkable role during the recent unrest in managing it behind the scenes.' While Jannati is not a member of the government or the judiciary, his words as the head of the Guardian Council and a close associate of the supreme leader carry some weight. At Friday prayer -- a forum Iran has often used to convey significant political messages -- he accused Britain of trying to provoke a 'velvet revolution.' As long ago as March, he said, the British Foreign Office had said street riots were possible during the June elections. 'These are signs, revealed by themselves,' he said. 