The British government announced on Monday that it will designate Iran’s Islamic Revolutionary Guard Corps (IRGC) as a state-backed security threat under new legislation, making it a criminal offence to support the organisation with a penalty of up to 14 years in prison. The bill, to be presented to Parliament this week, also targets proxies of Russia’s GRU military intelligence and an Iran-linked group accused of attacks on Jewish properties in London. The move marks the first use of powers under an amended National Security Act 2023 that allows the government to proscribe foreign state proxies deemed a threat to national security.

Iran’s Foreign Ministry condemned the decision on Tuesday as “unjustified, irresponsible and contrary to the fundamental principles and rules of international law”. Tehran described the IRGC as an inseparable part of its official armed forces and accused London of violating the UN Charter and interfering in Iran’s internal affairs. The ministry stated that Iran reserves the right to take reciprocal countermeasures under international law and warned that Britain would bear responsibility for the “destructive” political, legal and diplomatic consequences. Iranian officials linked the timing of the move to heightened tensions in West Asia, which they attributed to the actions of the United States and Israel.

Within the United Kingdom, the decision drew sharply divergent reactions. Andy Burnham, the presumptive incoming prime minister, praised the measure as “good”, arguing that supporting a group linked to death threats and attacks on UK soil should be illegal. Iranian Crown Prince Reza Pahlavi welcomed the designation and urged Western governments to go further in backing the Iranian people’s “fight for freedom”. By contrast, several left-wing MPs condemned the move. Zarah Sultana questioned why the Israeli Defence Forces were not similarly designated, while George Galloway claimed the legislation criminalised opinion and warned it set a precedent for restricting free speech. Viewed from Beijing, Chinese foreign ministry spokesperson Lin Jian expressed deep concern over the resurgence of military conflicts in the Gulf region and called on all parties to exercise restraint and protect innocent civilians.

The British government’s decision follows a series of antisemitic attacks in London earlier this year, including arson against synagogues and community ambulances, as well as a court case in which two Romanian nationals were jailed for a knife attack on a journalist from the Persian-language outlet Iran International. The court found the attack was carried out at Iran’s behest. The new legislation provides “proscription-like” powers to counter state threats including espionage, foreign interference, sabotage and physical attacks, according to the Home Office. The bill is expected to be debated in Parliament this week, while Iran has summoned the British ambassador in Tehran to protest what it calls “baseless accusations”.