The British embassy in Iran has been closed following an "outrageous" raid by students, and Iranian diplomats have been ordered to leave the UK within 48 hours, as tensions between Tehran and London intensify.
William Hague told the House of Commons on Wednesday it was "fanciful" the Iranian government did not know about an attack on the British embassy in Tehran on Tuesday.
"The majority of demonstrators were from a student Basij militia organisation. We should be clear from the outset that this is an organisation controlled by elements of the Iranian regime," he said.
David Cameron branded the Iranian government a "disgrace" for failing to protect staff at the embassy.
"The attack on the British Embassy in Tehran today was outrageous and indefensible. The failure of the Iranian government to defend British staff and property was a disgrace," he said.
Germany and France have recalled their ambassadors from Tehran in response to the incident, while across Europe Iranian ambassadors have been summoned to receive strong protests.
On Wednesday, the foreign minister of Austria said: “With the attack on the British Embassy, Iran is now on the verge of placing itself completely outside of the framework of international law.
"If Iran thinks it can undermine European solidarity through such actions, it is wrong. Officials in Teheran are called upon to implement their legal commitments and protect diplomatic facilities, with no ifs or buts”.
Iran said the decision to expel its diplomats from London was "hasty".
The latest developments come after increasing tension between Britain and Iran.
On Sunday the Iranian parliament voted to downgrade relations, which could see to British Ambassador expelled from Tehran. Iranian radio reported that some members of the Iranian parliament chanted "death to Britain" after the vote passed by an overwhelming majority.
Last week the British government said it was cutting its financial ties with Iranian banks over fears about the country's nuclear programme.
"We are doing this because of international evidence that Iran’s banks are involved in the development of Iran’s weaponised military nuclear weapon programme. We are doing this to improve the security not just of the whole world but of the national security of the UK", George Osborne said.
Tuesday's attack saw 200 protesters, including students and Basij militia, overrun the city-centre compound in Tehran. Once inside, the demonstrators set about vandalising and looting the homes of staff and the Ambassador.
A second British embassy located in the suburb of Gulhaq was also attacked and looted. Staff at the compound were unharmed.
All British consulate staff have since been accounted for.
A Foreign Office statement said that the intrusion was a violation of the Vienna Convention and a breach of Iran's international responsibilities, adding that however difficult relations between the two countries there is no excuse for "the failure to protect diplomatic staff and diplomatic premises".
In response to the incident, the UN Security Council issued a Statement condemning the attack and called on Iranian authorities to “protect diplomatic and consular property and personnel”.
Following the withdrawal of the British Ambassador, a leading academic on Iran has questioned the logic of Britain imposing sanctions on Iranian banks in response to the nuclear issue.
Speaking to the Huffington Post UK, Rosemary Hollis, Professor of Middle East Policy Studies at City University London, questioned the logic of still more sanctions in response to the nuclear issue, given that so far Iran has simply become more implacable.
“I was surprised to hear William Hague was to forge ahead with sanctions that would affect all and every British transaction with any bank in Iran,” she said.
“I hadn’t anticipated an invasion of the embassy compound, whether by students, or Basijees, and I don’t think the foreign office saw it coming but perhaps they should have."
“There’s a lot of history between the two countries, and the Foreign Office has had a lot of practise dealing with Iran.”
“The Iranians are more prickly about Britain than any other nation, including the Americans. There was the Salman Rushdie affair, endless fuss about BBC Persian Service, the British sailors… so I’m not sure the latest British measure vis-à-vis the banks has taken full account of the very particularl dynamics of British Iranian relations.”
Hollis also questioned the effectiveness of British sanctions on the banks leading to a change in Tehran’s nuclear policy, or even Britain taking the lead in that move given the state of relations between the two nations.
“We’ve lived with the spectre of war with Iran for the past few years, but I think we need to be very careful we don’t end up in one without sitting down to think about it and make a deliberate decision to choose it first,” she warned.
According to Abraham Wagner, Professor at Columbia and a foreign policy adviser to Newt Gingrich, the UK was left with little choice but to close its embassy.
Speaking to The Huffington Post UK, Wagner said:
"As many have stated in the past few days, this attack on an embassy is totally unacceptable under established international norms, and comes from or was condoned by the same regime that took over the US Embassy in 1979, holding US diplomats hostage for many months. The Iranian regime simply has no respect for international law or diplomatic protocol."
Looking forward, Wagner said it would be important to see whether this was sponsored or just condoned by the President or the Supreme Ayatollah.
"Was it a situation that simply got out of control and was not properly constrained, as in the case of the Israeli Embassy in Cairo last September, or was there more involved?"
He added that the storming of the embassy would not have an immediate impact on the security of the region, "other than showing that Iran is less stable and not a responsible international actor".
Long term, however, Iran's actions "do not bode well for regional stability," he said.