The appointment of former NSW deputy premier John Barilaro as the state's trade commissioner to the US will be investigated by a parliamentary inquiry.

His new job as trade commissioner was announced on Friday and is among six trade posts around the world tasked with spruiking the state's investment opportunities and local businesses.

Premier Dominic Perrottet said Mr Barilaro's appointment was the result of a "rigorous talent search" by a global recruitment firm.

Mr Barilaro, who resigned late last year just days after former premier Gladys Berejiklian, played a role in setting up the international trade initiative Global NSW.

Opposition Leader Chris Minns said an upper house inquiry would now look into the decision, which he has described as a "$400,000-a-year job for a friend".

"This represents everything that's wrong with the NSW Liberals and Nationals after 11 years in government," he said on Twitter.

"This is Dominic Perrottet's captain's pick and he will be held accountable."

Penny Sharpe, Labor's leader in the upper house, said the inquiry would leave no stone unturned.

"This stinks to high heaven," Ms Sharpe said.

"It just doesn't make any sense that the Premier would decide that John Barilaro is the best person in the whole of NSW to go to New York and represent us on our behalf."

Treasurer Matt Kean today defended the decision-making process regarding the appointment.

"John Barilaro was a trade minister and he appears qualified to be a trade commissioner," he said.

"I've been informed that this has gone through the proper process and that's how decisions should be taken."

In accepting his appointment, Mr Barilaro — who recently settled his defamation case against Google — said he would continue to build on what had already been achieved.

"I'm looking forward to supporting NSW companies to export and expand to the United States," he said.

"Including the many fintech, cyber security, space, health and food and beverage companies. 

Mr Barilaro, a former Monaro MP, resigned last year, saying public life had "taken a toll".