Federal Climate Change Minister Greg Combet will today be questioned at the Independent Commission Against Corruption (ICAC) about a controversial mine proposal.

Mr Combet is not accused of any wrongdoing, but is expected to be asked about a letter of support he wrote for a training mine in the New South Wales Hunter Valley.

The ICAC alleges former NSW Labor minister Ian Macdonald 'gifted' the Doyles Creek licence to former union official John Maitland without a tender.

The inquiry has heard that although the project was promoted as a training mine, it was really a commercial venture intended to benefit Mr Maitland and a small group of businessmen.

Mr Combet's letter of support, which has already been presented to the ICAC said: "The proposal by Doyles Creek Mining to develop a world-class training facility in the Hunter Valley, in the event that an underground mine proceeds, will in my view make a significant contribution to meeting the skills shortage that exists in the mining industry."

He was also supportive of the involvement of the Westpac Rescue Helicopter Service, Newcastle University and the Hunter Valley Training Company in the project.

Mr Combet was elected as federal member for Charlton in 2007 and was previously head of the Australian Council of Trade Unions.

Yesterday NuCoal Resources - the company that now owns the Doyles Creek licence - confirmed that one of its directors, Mike Chester, has resigned.

When presenting his evidence to ICAC in April Mr Chester denied lying about amounts of money and denied writing two bogus letters to support Doyles Creek as a training mine.

In one letter he was accused of falsely stating $5 million equity had been raised, but Mr Chester said that was not a lie because he knew the investors would eventually come up with the money.

In a surprise development yesterday former Labor minister Eddie Obeid was recalled to the ICAC to give evidence next week related to a separate inquiry into the Mount Penny licence.

A public inquiry into the Mount Penny licence has finished hearing evidence but the ICAC says a complaint has been raised on Mr Obeid's behalf that evidence previously given by witness Alan Fang had not been put to him.

An ICAC statement says: "Irrespective of whether or not it was necessary to do so, the commission has decided that Mr Obeid Sr should be recalled so that these issues can be raised with him by counsel assisting the commission."