Tempers have frayed at the corruption watchdog as sidelined NSW minister Chris Hartcher angrily rejected suggestions he had been “instrumental” in setting up a sham company to wash funds from banned donors.

Mr Hartcher appeared before the Independent Commission Against Corruption (ICAC) to reject claims from counsel assisting Geoffrey Watson SC that he masterminded a Liberal slush fund scam and used his own nephew’s law firm to launder money.

ICAC has been investigating a “sham” company set up by Mr Hartcher’s former staffer, Tim Koelma, which allegedly issued fake invoices to disguise political donations from property developers, including Sydney’s Gazal family and former coal mogul Nathan Tinkler’s Buildev.

Commissioner Megan Latham was forced to step in as the two men clashed over suggestions Mr Hartcher used his solicitor nephew Sebastian Reid to launder $4000 in Liberal Party donations through the family law firm, Hartcher Reid, and then through another business, Mickey Tech.

“I’m putting to you that you pocketed the $4000,” Mr Watson said.

“I reject that absolutely,” Mr Hartcher said.

“I reject it absolutely and I resent it.”

“Don’t you dare tell me you resent anything I say,” Mr Watson bellowed, as Mr Hartcher’s brief repeatedly called for a time-out.

“Can we all just back off right now,” Ms Latham said.

“I don’t want things to degenerate into a screaming match.”

Neither Mr Reid nor his law firm are accused of any wrongdoing.

The former resources minister, who resigned from cabinet after ICAC officers raided his office late last year, also rejected allegations he asked staffer Ray Carter – whose partner’s company Mickey Tech is said to have been used as a conduit in the alleged cheque-laundering scam – to lie to the corruption watchdog.

Mr Hartcher said he had tried to “stretch his memory”, but he could not recall elements of the alleged transaction.

But Mr Watson said telephone records, bank documents and Mr Reid’s sworn testimony were compelling.

“I’m giving you an opportunity to explain it away, Mr Hartcher,” Mr Watson said.

“Fairness – that’s my middle name.”

The inquiry continues.