Prosecutors have charged a former senior FBI officer with sanctions-busting for carrying out private investigation work for oligarch Oleg Deripaska in a potential sign of the future direction of US sanctions enforcement.

The US Department of Justice alleges that Charles McGonigal breached sanctions after being paid to investigate one of Deripaska’s rivals in a struggle for control of a large Russian corporation. McGonigal, who started working for Deripaska after quitting the FBI after 22 years, has denied sanctions breaches and money laundering.