Former prime minister Tony Abbott (Image: AAP/Dean Lewins)

An Inq investigation into a billionaire climate sceptic's Liberal Party backing speaks to the way Australia's pitiful political donations regulations "very much run counter to democratic principles", a political donations expert has told Crikey.

The investigation uncovered that Michael Hintze, a leading free marketeer and sceptic of the role of carbon emissions in climate change, donated $75,000 to former prime minister Tony Abbott's 2013 election campaign (amongst other Liberal Party support over the years), and has had a long-running business relationship with Energy Minister Angus Taylor.

Both Abbott and Taylor have led Coalition attacks on the idea of government support for renewable energy.