Once second only to Ferdinand Piech, Volkswagen's then-chief executive, who is currently chairman, Volkert stepped down when it came to light that he had also pocketed nearly $2.96m in illegal bonuses.
The court on Friday also handed down a one-year suspended sentence to Klaus-Joachim Gebauer, a former personnel manager and aide to Hartz for breach of trust.
Gebauer organised numerous events at which Volkswagen labour representatives were extensively wined and dined and even took trips to nightclubs and brothels paid for by a corporate slush fund.