“Iranian state actors and their proxies are already active inside the UK,” they said.
The warning follows an arson attack in Golders Green on Monday, in which four Hatzola ambulances were torched, an act later claimed by an Iran-linked group. Two people have been arrested and released on bail over that incident.
Just days earlier, two men had been charged in a separate case involving alleged surveillance of Jewish targets in London on behalf of Tehran.
Additionally, an Iranian man arrested after allegedly trying to enter the Faslane naval base on March 19 has been released pending further inquiries.
Earlier this year, the IRGC played a leading role in the brutal suppression of protests that erupted throughout Iran, resulting in the killing of an estimated tens of thousands of people, the largest massacre in the modern history of Iran. The IRGC is also believed to be behind a concerted campaign against Iranian dissidents living abroad, including Britain.
A person holds up a placard which reads 'IRGC (Islamic Revolutionary Guard Corps) terrorist. UK: Put them on the list. Proscribe them!' as they take part in a London rally in solidarity with protesters in Iran, January 11, 2026 (Credit: Alishia Abodunde/Getty Images)Getty Images
Prime Minister Sir Keir Starmer has taken a cautious line after being advised that outlawing an organisation tied to a foreign state could prove legally fraught, despite backing a ban while in opposition.
Currently serving officials in the Foreign Office and MI6 reportedly harbour doubts about proscription, concerned that such a move could shut down the already fragile diplomatic channels with Tehran.
The group of former intelligence figures dismiss the concern that proscription would reduce Britain’s influence in Tehran as “unconvincing”.
“In reality, Britain today exercises negligible influence over Iran. If anything, the dynamic increasingly operates in the opposite direction,” they write.
Sir Ken McCallum, MI5’s director-general, revealed in October that they had stopped more than 20 Iran-linked plots on British soil in the last year. Intelligence sources anticipated that that number would increase amid the current conflict.
The global terrorism index said this month the IRGC was behind 157 terrorist plots across 15 countries in the past five years. Since the death last month of Ali Khamenei, Iran’s supreme leader who commanded absolute control of the IRGC, the group has increasingly operated in a fragmented and autonomous manner.
The UK has sanctioned the IRGC “in its entirety” according to Starmer, but has stopped short of formally banning it as a terrorist organisation.
