"A decision has been made to revoke Janse Van Rensburg's accreditation, and he has been ordered to leave Russia within two weeks," the FSB said in a statement.
During its counterintelligence activities, the FSB identified an undeclared UK intelligence presence under the guise of the British Embassy in Moscow.
An FSB investigation revealed that the second secretary had intentionally falsified information on his entry application, a direct violation of Russian law. In addition, the bureau identified signs of Rensburg's involvement in intelligence and subversive activities that posed a threat to Russia's security.
Deputy British Ambassador to the Russian Federation Danae Dholakia was summoned to the Russian Ministry of Foreign Affairs.
The Russian Foreign Ministry said that it had expressed protest to UK Charge d'Affaires in Moscow Danae Dholakia due to the embassy employee providing false information upon entry to the country.
"On March 30, the Russian Foreign Ministry summoned UK Charge d'Affaires in Russia Danae Dholakia and expressed a strong protest over the revelation that one of the UK Embassy's diplomatic staff had provided false information about themselves when applying for permission to enter Russia," the ministry said in a statement.
Moscow will not tolerate activities of undeclared UK intelligence officers in the country and will respond immediately if London escalates the situation over the revocation of the accreditation of its embassy employee, the statement read.