Nathan Tinkler has arrived at the ICAC in Sydney but is not expected to give evidence until tomorrow amid allegations he donated thousands of dollars to the Liberal Party and tried to bribe a Labor MP.
Tinkler and his legal counsel arrived at the ICAC building just after 2pm.
The former billionaire coal mogul is expected to face questions over whether his Buildev property development group donated $60,000 to a secret Liberal Party slush fund before the 2011 state election.
The money was allegedly used to bankroll Newcastle Liberal MP Tim Owen’s election campaign.
Tinkler is also alleged to have offered a bribe to former Labour MP Jodi McKay. It is claimed after she refused, Buildev paid to have leaflets smearing her campaign distributed in her electorate.
The inquiry heard that Tinkler's Buildev had plans for a coal loader at Mayfield in Newcastle.
Property developers have been banned from donating to political parties since 2009.
Former police minister Mike Gallacher, who was the minister for the Hunter, quit in early May after it was alleged he "hatched a corrupt scheme" with Buildev executive Darren Williams to move money into the fund.
The money is alleged to have come from Tinkler's horse stud, Patinack Farm, with a further $20,000 donated to the Nationals using four former workers at his company Aston Resources, SMH reported.
Tinkler’s evidence will become part of a wider investigation into allegations former energy minister Chris Hartcher and fellow central coast MPs Chris Spence and Darren Webber took hundreds of thousands of dollars in donations in return for political favours.
It is alleged a fake company, Eightbyfive, was set up by Tim Koelma, who was an adviser to Hartcher.
All four MPs voluntarily withdrew from the Liberal Party before the start of the most recent ICAC hearing, Operation Spicer.
It is alleged that between 2009 and 2011 nine companies paid $414,042 to Eightbyfive.
In an email tendered at the ICAC earlier this month, Tinkler complained that he had “dontated [sic] to the nats" and they were doing "f— all" to approve a plan by Buildev to build a new billion dollar coal terminal in Newcastle.
"We had a bunch of deadbeats before and now we have a bunch of pr–ks scared to make a decision," an email sent by Tinkler in 2011 read.
When ICAC started the investigation, Tinkler emailed a college in 2013 asking: "Who is ICAC?"
Owens said on Monday that he would no recontest the 2015 election has it was “highly likely” Buildev threw money at his election campaign.
Greens MP John Kaye said the ICAC allegations should lead to a review of all the decisions made by Chris Hartcher while in office.
"The allegations throw a serious cloud over every decision that Mr Hartcher was involved in," Kaye said.