Former NSW Labor minister Ian Macdonald was out at lunch for several hours each week when his department was considering a tender process for coal exploration licences in the Hunter Valley, a corruption inquiry has heard.

Mr Macdonald also told the inquiry he didn't think that the allotting of coal mining tenements should have been of "paramount importance" to him as mining minister.

Mr Macdonald was giving evidence for a fourth day on Thursday at the Independent Commission Against Corruption (ICAC) inquiry into the opening up of coal mining in the NSW Bylong Valley in 2008.

He is alleged to have rorted a tender process for coal mining exploration licences to benefit his former Labor colleague Eddie Obeid, whose family owned land around Mt Penny where a critical coal tenement was created.

On Thursday, Mr Macdonald said he did not interfere with a department of primary industries committee that was working on the tender process in 2008.

"It never came to my mind that I should be going in there and telling the department what to do with committee processes," he said.

Soon afterwards, Commissioner David Ipp said: "I don't mean to be rude but this is a serious question, at this time were you not spending several hours in the week having lunch?"

Mr Macdonald replied: "Mr Commissioner, if I had lunches in that period, and clearly I did, they would be work-related lunches."

"I was invited to those by those people" he went on say, to which Mr Ipp replied: "so what?"

Mr Ipp suggested the allotting of coal mining tenements in the Hunter "should have been of paramount importance to you as mining minister".

"I disagree with you," Mr Macdonald replied.

ICAC alleges the now disgraced former minister stood to receive millions of dollars for favours.

Mr Macdonald maintains the critical Mt Penny tenement was created "by chance" over Obeid land after he found the area in an atlas.

Mr Macdonald has previously been branded "Sir Lunchalot" in the media.

The inquiry continues.