British Prime Minister Andy Burnham told parliament on Monday that a suspected plot against RAF Fairford was "highly likely" to have been coordinated in Iran, and that the Islamic Revolutionary Guard Corps had almost certainly directed it.
"I can confirm our assessment that it is highly likely to have been coordinated in Iran, almost certainly directed by Iran's Islamic Revolutionary Guard," Burnham told MPs, in remarks carried by Al-Monitor. He added: "We will not tolerate these threats on our soil."
The Gloucestershire airfield has hosted US bombers flying strikes on Iran. President Donald Trump said last week that an Iran-linked threat had led to the withdrawal of American B-1 aircraft, and US officials told Reuters they were looking at a suspected drone attack plan.
Burnham set out the assessment in the Commons, in a video published by the Global Broadcasting Service.
Counterterrorism police detained five British men in their twenties close to the base before dawn on 27 September, on suspicion of terrorism and explosives offences. Officers found petrol in the vans they had been travelling in but no usable explosive, and said they were investigating possible involvement by a foreign state.
All five were freed without charge on bail with stringent conditions, RTE reported. Two further men, one of them a British-Iranian national, were also held and released, bringing the total arrested and bailed to seven, according to The Independent.
Burnham said his government would "crack down on Iran's use of criminal networks", go after their funding and impose more sanctions to curb the IRGC's ability to act. The Independent reported that Britain summoned Iran's ambassador on Monday, citing Tehran's continued efforts to damage UK security through criminal networks, proxy groups and state-backed activity.
Iran denies any role, calling the claims "unfounded and malicious speculations". Britain used new counter-proxy powers in July to outlaw support for the IRGC and an affiliated group it blames for attacks on sites tied to Jewish and Israeli communities and to Persian-language media.