"All of Iran's attempts to threaten, silence, intimidate, harass, harm or coerce people in our territories through proxies or other means are unacceptable," reads a joint statement, also backed by France, Germany, Canada and Sweden, among others.
The statement follows an incident at RAF Fairford at the end of September, when several people were arrested on suspicion of plotting terrorist attacks.
British Prime Minister Andy Burnham reiterated on Monday in Parliament that there were "strong indications" that Tehran was involved in the incident.
"I can confirm that in our assessment it was most likely coordinated in Iran and that it was almost certainly through the agency of the Iranian Revolutionary Guard," Burnham said, according to Sky News.