Mining magnate Travers Duncan has launched legal action against the New South Wales corruption watchdog in a bid to stop its commissioner making any adverse findings.

The claim was first heard in the NSW Supreme Court on Thursday and lists the Independent Commission Against Corruption (ICAC) and Commissioner David Ipp as defendants.

It is understood Mr Duncan could be financially affected by any findings the commissioner makes against former Labor Minister Eddie Obeid and his coal mining interests in the Bylong Valley.

The corruption inquiry into the activities of Mr Obeid and former Labor minister Ian Macdonald finished hearing evidence on Thursday.

ICAC has spent the past three months investigating allegations Mr Macdonald rigged a 2008 tender process for a coal licence in the NSW Upper Hunter to benefit Mr Obeid.

The inquiry also heard from Mr Duncan.

Mr Duncan's legal bid is set down for a hearing in the Supreme Court later this month.

Commissioner Ipp is expected to hand down the findings from the corruption inquiry in July.