Rishi Sunak is facing cross-party pressure to proscribe Iran’s Islamic Revolutionary Guard Corps (IRGC) as a terrorist group after Tehran’s assault on Israel over the weekend. The shadow defence secretary, John Healey, and the former Conservative leader Iain Duncan Smith accused the government of being slow to act in the face of evidence of a growing risk to UK interests. Ministers are said to have the issue under review, but it has been argued within government that the security services need to keep points of contact with the Iranian authorities. Healey said the threat to the UK from allowing the IRGC to operate should be sufficient for the government to follow the US government in banning the organisation. He said: “We’ve been arguing this case for well over a year now that the Iranian Revolutionary Guard, which was at the forefront of the Iranian attack, should be proscribed to this country. It is responsible; it’s the leading edge of the threat that Iran poses not just to Israel, but to Arab countries and western interests right across the region. “It’s the way that the Iranians sponsor and support violent military militia groups that destabilise the region and threaten other countries as well.” Duncan Smith, who was one of 90 Tory MPs to sign a letter calling for a ban last year, said he understood that the US had asked Downing Street to proscribe the group, as he described ministers’ justifications for failing to do so as “absurd”. He told the Guardian: “The government should have already proscribed IRGC. The USA have asked us to do it. The excuses the government uses are [firstly] that if the UK proscribes the IRGC it will lose influence. That’s absurd as we clearly have no influence. [Secondly that] the USA needs us an interlocutor. But the USA doesn’t agree as they have already asked us to proscribe the IRGC.” Confronted in the Commons by Duncan Smith, the prime minister responded: “We are urgently working with our allies to see what steps we can take together in a co-ordinated fashion to deter and condemn what Iran is doing.” The foreign secretary, David Cameron, said the government was considering its options. Asked whether the government would consider further sanctions against Iran, he told the BBC: “Yes, absolutely. We already have 400 sanctions on Iran. We put in place a whole new sanctions regime at the end of last year, which is proving very effective. “We’ve sanctioned the IRGC … in its entirety, and we’ll continue to look at what further steps we can do.” He later suggested that a change in approach was not imminent, telling LBC “the police and our intelligence services say they have the powers already to deal with IRGC action, either here or elsewhere.” No 10 also intimated that it would resist the calls. A Downing Street spokesperson said a diplomatic presence in Iran was “one of our most effective channels for avoiding escalation”, and enabled “robust messages” to be delivered. When asked by the shadow home secretary, Yvette Cooper, in the Commons whether the government would proscribe the IRGC, her counterpart, James Cleverly, said he would not speculate. “We keep our response to Iran consistently under review and of course we have done so in the light of the attacks in Wimbledon,” he said. “But she will also know that we do not speculate about future designations or sanctions.” The IRGC was established after Iran’s 1979 revolution to defend the country’s Islamic system and to act as a counterweight to the army. It has become a major military, political and economic force in Iran but its estimated 190,000 personnel also act outside the country. In January, the UK imposed sanctions on individual members of the IRGC’s Unit 840 over plots to assassinate two television presenters from the news channel Iran International on British soil. The government said at the time that the plot was “just the latest credible reporting of the regime’s attempt to intimidate or kill British nationals or UK-linked individuals, with at least 15 such threats taking place since January 2022”. Bahrain, Saudi Arabia, Sweden and the US have already designated the IRGC as a terrorist organisation. On Sunday, Lior Haiat, a spokesperson for the Israeli ministry of foreign affairs, demanded a ban on the IRGC as an “initial price” for its “large-scale and unprecedented” aggression. In a letter to the British prime minister on Monday, the president of the Board of Deputies of British Jews, Marie van der Zyl, wrote of a “direct threat” to the Jewish community and Iranian dissidents in the UK, as she praised the role of the RAF in protecting Israel from the Iranian bombardment on Saturday night. The letter said: “I am also writing on behalf of the British Jewish community to reiterate our request that the Iranian regime’s IRGC – Islamic Revolutionary Guard – be proscribed as a terrorist organisation in its entirety. The IRGC’s role in funding, arming and training a host of terror proxies, including Hamas, Hezbollah and the Houthis is clear.” In April last year, 125 MPs – including more than 90 Conservatives – signed an open letter calling for the organisation to be proscribed. Within government, the security minister, Tom Tughendhat, has been supportive of proscribing the IRGC, while the home secretary is understood to have voiced doubts about such a move.