A man from London and another from Oxfordshire have been charged with spying for China.
Christopher Berry, 32, of Witney, and Christopher Cash, 29, of Whitechapel, are accused of breaching the Official Secrets Act and passing on “information prejudicial to the safety or interests of the State”, the Metropolitan Police said.
The force described it as an "extremely complex investigation" into “very serious allegations”.
The two men have been bailed to appear at Westminster Magistrates' Court on Friday 26 April.
Commons Speaker Sir Lindsay Hoyle has told MPs one of the men, Mr Cash, was a Parliamentary pass holder.
He told the Commons: “This morning two people were charged with offences under the Official Secrets Act of 1911. One of those individuals was a Parliamentary pass holder at the time of the alleged offences.
“This matter is now sub judice. Under the terms of the House’s resolution on matters of sub judice members should not refer to it in the chamber.
“I know that honourable and right honourable members will understand how important it is that we do not say anything in this place that might prejudice a criminal trial relating to a matter of national security.”
Commander Dominic Murphy, head of the Met’s Counter Terrorism Command, said: "This has been an extremely complex investigation into what are very serious allegations.
"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 two men were originally arrested in March last year in connection with the investigation.
Nick Price, Head of the CPS Special Crime and Counter Terrorism Division, said: "The Crown Prosecution Service Counter Terrorism Division has today authorised the Metropolitan Police to charge two men with espionage offences.
"Christopher Berry, 32, and Christopher Cash, 29, will be charged with providing prejudicial information to a foreign state, China, and will appear at Westminster Magistrates’ Court on Friday April 26.
"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."
