New South Wales premier Dominic Perrottet has admitted he knew for months John Barilaro was in the running for a $500,000 a year trade role in New York. 

Barilaro's appointment as the NSW Senior Trade and Investment Commissioner to the US, a position he created when he was trade minister, has come under immense scrutiny from ministers.

The former deputy premier's appointment to the sought-after role comes just six months after he resigned from politics.

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Perrottet today conceded Barilaro told him personally he wanted the role at a social function.

"In a social setting he may have said that he was applying for a position, for which there was an independent process," Perrottet said.

Perrottet claimed he gave Barilaro no feedback on whether he thought the appointment to the role was appropriate.

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He is also adamant that Barilaro was not promised the role when he was still in parliament. 

"John Barilaro is a former trade minister who went through an independent process," Perrottet said.

"There was no talk about a future job in terms of why he was resigning."

Perrottet has now ordered an independent review of the appointment process to provide "public confidence" in the government's decision-making.

Meanwhile, a parliamentary inquiry examining the hiring process begins tomorrow.