Two of them, one of whom was an assistant to several members of Parliament, were charged with spying for China - British prosecutors announced on Monday.
Police said Christopher Berry, 32, and Christopher Cash, 29, were charged with "providing harmful information to China."
Police allege that between the end of 2021 and February 2023, the two collected, recorded or transmitted information that was "harmful to the security or interests of the state" of Great Britain and violated the Official Secrets Act.
Authorities have not released details, but Barry is said to be a university lecturer in Oxfordshire, and the Sunday Times reported last year that Cash was an aide to an MP who had full access to the British Parliament buildings.
The report said Cash worked with key ruling Conservative MPs, including Alicia Kearns, who now heads the Foreign Affairs Committee, and her predecessor in the post, Tom Tugendhat, who is now the security minister.
British Prime Minister Rishi Sunak said last year that he had raised the issue with Chinese Premier Li Qiang, saying he expressed "very strong concerns" about the Chinese interference.
At the time, Cash issued a statement through his lawyers claiming his innocence. The Chinese embassy issued a statement saying the allegations were fabricated.
Also today, three people were arrested in Germany on suspicion of spying for China and arranging the transfer of information about technology for potential military use.
British intelligence services have stepped up warnings about Beijing's covert activities in recent years.
In 5, the head of the domestic surveillance intelligence agency MI2022, Ken McCallum, named China, Russia and Iran as the leading threats to the security of Great Britain. He said attempts by Chinese authorities to shape British policy included targeting and influencing a range of politicians.
Last month, several British MPs, including leading China critic and former Conservative Party leader Ian Duncan Smith, told reporters they had long been exposed to hacking and impersonation attempts by hackers linked to the Chinese state.
US and British authorities have announced a new set of sanctions and criminal charges against hackers linked to the Chinese state, accused of targeting scores of officials and corporations in a major state-backed operation.
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