The NSW corruption watchdog will resume its inquiry into a tainted coal deal linked to the Obeid family and former Labor minister Ian Macdonald on Monday.

The Independent Commission Against Corruption (ICAC) is probing whether former Labor minister Ian Macdonald rigged a 2008 tender process for a coal exploration licence in the NSW upper Hunter, and how Labor powerbroker Eddie Obeid may have profited from it.

Mr Macdonald is accused of doing the bidding of Obeid family members, who allegedly hid their involvement through complex trust and company structures.

The inquiry has heard that the Obeids stood to make $100 million from mining deals in the area.

The inquiry has already already heard from former NSW premiers Nathan Rees and Morris Iemma as well as a number of Obeid family associates.

ICAC is still to hear evidence from key members of the Obeid family, including Eddie Obeid, as well as from Ian Macdonald.

The inquiry, presided over by Commissioner David Ipp, is expected to conclude in February.