Another union official is expected to give evidence today at an inquiry into a mining licence approved by former New South Wales Labor minister Ian Macdonald.

The Independent Commission Against Corruption (ICAC) is investigating the Doyles Creek licence he approved for former union boss John Maitland in 2008.

Today Construction Forestry Mining and Energy Union (CFMEU) official Ian Murray will give evidence.

Yesterday CFMEU national president Tony Maher told the ICAC he was approached to sign documents supporting a proposed training mine at Doyles Creek in the Hunter Valley.

But he said he refused because he thought it would end in scandal.

Another witness at the inquiry yesterday, Labor Senator Doug Cameron, said he did not support an attempt to strip Ian Macdonald of his preselection in 2006 because he thought he was a competent minister.