In late June, Zharko voluntarily surrendered to Russian authorities, disclosed the names of four British intelligence officers, and revealed locations in Europe where alleged clandestine meetings had taken place, including information regarding the assignments he had been given.
The FSB later launched a criminal investigation into British intelligence officers' operations on Russian territory from 2003 until 2007.
"During the investigation, witness Vyacheslav Zharko identified MI6 operative Pablo Miller, who was previously involved as a suspect in a criminal case against Sergei Skripal, a former Russian colonel sentenced last year to 13 years in prison for spying for Britain," an FSB spokesman said.
According to the spokesman, Zharko knew his recruiter and tutor as an individual named Paul. However, Skripal earlier identified the same individual as a certain Antonio Alvares de Idalgo.
The investigation has established that Paul is MI6 intelligence operative Pablo Miller, who worked in 1999 under the cover of the First Secretary at the British Embassy in Tallinn and was involved as a suspect in a criminal case against Valery Ojamae, a former Russian intelligence officer who was jailed in 2001 for seven years after being convicted of spying for Britain and Estonia.
Ojamae was charged in March 2000, followed by a spy row in August 1999 in which Russia and Estonia each expelled two diplomats from their countries.