Britain's foreign ministry on Monday summoned Iran's ambassador to London, Seyed Ali Mousavi, criticizing what it called Tehran's "reckless and destabilizing actions" in the UK and overseas.
"The summons follows the recent charging of two individuals, one Iranian national and one British-Iranian dual national, under the National Security Act, on suspicion of providing assistance to a foreign intelligence service," a Foreign Office spokesperson said.
"This government will take all measures necessary to protect the British people, including exposing Iran's reckless and destabilizing actions at home and abroad," the spokesperson added.
Two Iranians appeared in court in London on Thursday accused of spying on the Jewish community in London on behalf of Tehran, including by allegedly carrying out reconnaissance of potential targets such as a synagogue.
UK police, the domestic MI5 intelligence service and members of parliament have long warned about a growing threat from Iran, which is currently locked in a war with the United States and Israel.
Nematollah Shahsavani, 40, a dual Iranian-British national, and Alireza Farasati, 22, an Iranian citizen, are charged with engaging in contact likely to assist a foreign intelligence service between July 9 and August 15 last year.
Prosecutor Louise Attrill told the court last week the pair were "suspected of assisting the Iranian intelligence service by conducting hostile surveillance of locations and individuals linked to the Israeli and Jewish community".
Police on Saturday also said an Iranian man, along with a Romanian woman, had been charged over attempting to enter a Royal Navy base where Britain's nuclear submarines are based.
The pair were arrested for trying to breach the Faslane base in Scotland on Thursday, which houses the UK's Trident nuclear deterrent, made up of four submarines armed with Trident ballistic missiles.
The Iranian man has since been released from custody pending further inquiries, Scotland's public prosecution service said in a statement on Monday.
The service added there would be "no proceedings" against the Romanian woman, 31, although it reserved "the right to proceed in the future should further evidence become available".
There are fears in Britain the country could become a target over its role in the US-Israeli war on Iran.
Britain has authorized American forces to use two of its bases for some US operations against Iran, which the British government insists are purely "defensive".
