The Federal Security Service (FSB) planted the bug as part of its investigation into whether senior officials at the Russian Investigations Committee (SKR) were taking bribes.

The covert operation eventually led to three arrests, including the head of the SKR’s internal security directorate, Mikhail Maksimenko.

The trio insist they did not implicate themselves in the recordings, which one of the three dismissed as “the prattle of tipsy men”.

However, Russian authorities are confident a court in Moscow will agree the recordings prove they took bribes from a known crime kingpin.