- They are accused of giving "articles, notes, documents or information" to a foreign state, the Met Police said.
- Police called it an "extremely complex investigation into what are very serious allegations".
Two men have been charged with spying for China after allegedly providing information which could be "useful to an enemy".
Christopher Berry, 32, and Christopher Cash, 29, were charged under the Official Secrets Act.
They are accused of giving "articles, notes, documents or information" to a foreign state, the Met Police said.
Police called it an "extremely complex investigation into what are very serious allegations".
Cdr Dominic Murphy, head of the Counter Terrorism Command, said: "We've worked closely with the Crown Prosecution Service as our investigation has progressed and this has led to the two men being charged today.
"We're aware there has been a degree of public and media interest in this case, but we would ask others to refrain from any further comment or speculation, so that the criminal justice process can now run its course."
The Met said officers previously arrested two men on 13 March 2023 in connection with the investigation. A man in his 30s was arrested at an address in Oxfordshire and a man in his 20s was arrested at an address in Edinburgh, they said.
Both men were subsequently released on police bail while the investigation continued and a case file was passed to the CPS for consideration in late 2023.
The charges against Mr Berry, from Witney in Oxfordshire, are alleged to have happened between 28 December 2021 and 3 February 2023, while the charges against Mr Cash, of Whitechapel, London, are alleged to have happened between 20 January 2022 and 3 February 2023.
The charge states that "for a purpose prejudicial to the safety or interests of the state, obtained, collected, recorded, published, or communicated to any other person articles, notes, documents or information, which were calculated to be, might be, or were intended to be, directly or indirectly, useful to an enemy".
The two men have been bailed to appear at Westminster Magistrates' Court on Friday 26 April.
Nick Price, head of the CPS's Special Crime and Counter Terrorism Division, said in a statement: "Criminal proceedings against the defendants are active. No-one should report, comment or share information online which could in any way prejudice their right to a fair trial."