Mining magnate Travers Duncan most likely passed on a leaked government document about the opening up of coal mining in the NSW Hunter region, a corruption inquiry has heard.
It is also investigating whether former state Labor minister Eddie Obeid and his family gained substantial financial benefit from the move.
The ICAC heard evidence on Tuesday from John McGuigan, a shareholder in Cascade Coal and former director of White Energy, which made a failed $500 million bid for Cascade, the eventual winner of the controversial tender.
The inquiry has heard the Obeids were allegedly paid $30 million for their 25 per cent stake in Cascade.
Mr McGuigan said on Tuesday that Mr Duncan probably gave him a leaked document, which he handed to his son James in November 2008.
Only high-ranking officials inside the Department of Primary Industries should have had access to the document, the inquiry has been told.
"I did not have direct relationships with the department, and I think the likely source is that I got the document from Mr Duncan," Mr McGuigan said.
While nominating Mr Duncan as a likely source, Mr McGuigan said he couldn't clearly recall where he got the document.
"The number of sources are pretty limited, but I've racked my memory and I don't have a clear and precise recollection," he said.
Mr McGuigan said he didn't know the document was confidential at the time he had it.
He also said he was aware that Mr Duncan and Mr Macdonald knew each other and they had a "relationship that was primarily through business".
He conceded that he knew by May 31, 2009, that the Obeid family was involved in mining in the Bylong Valley.
By early 2010, he said, there was a "strong view that we had a major problem with this particular project if the Obeids continued to retain their equitable interest".
He said there was "some concern" that the Obeids' previous involvement in the Mt Penny coal tenement "may prejudice the grant of a mining lease" over the area.
"We obviously hope that would not be the case," he said.
Earlier, Barry Gregory, who used to manage the Obeids' property, Cherrydale Park, said that in the two years he worked there he saw Eddie Obeid only a handful of times.
"I only saw old Eddie there three or four times," Mr Gregory replied.
He agreed with counsel's suggestion that the property wasn't a "weekender" for the Obeids.