It was November 2011 when Ian Macdonald's role in awarding a coal licence to Doyle's Creek Mining was first referred to the NSW corruption watchdog for its close attention.

Unusually, the mechanism was a vote of both houses of the NSW Parliament, ensuring that the Independent Commission Against Corruption conducted a full investigation.

The motion was introduced to the Legislative Assembly by the new Coalition government's then energy and resources minister, Chris Hartcher.

The move followed a report commissioned by the department of resources and energy from law firm Clayton Utz, which found "a circumstantial case of wrongdoing".