The NSW Labor opposition and Greens have called for NSW Treasurer Dominic Perrottet to stand aside after his chief of staff Nigel Freitas resigned on Friday over the scandal involving icare, the beleaguered state-owned insurance agency.

John Nagle, the chief executive and managing director of icare, quit last week amid reports of poor financial management at the company and a statutory five-year review of the company's workers' compensation scheme was expedited.

It was then revealed on Friday that two of Mr Perrottet's ministerial staffers were paid by icare and on secondment from the company, signed off by Mr Freitas.

Mr Perrottet defended the staff secondment to his office and said secondment from government sector agencies like icare to ministerial offices was allowed, but he regretted that an administrative error had occurred in this case.

He said he was told of the error on Wednesday after Mr Freitas was informed by icare that the correct documentation had not been provided.

Ms Berejiklian on Monday told reporters her office had no knowledge of the secondment and it was arranged between Mr Perrottet's office and icare.

She declined to answer questions about icare as the statutory review was underway and NSW Treasury Secretary Michael Pratt AM had also been asked to audit the office.

"I do have confidence in the treasurer, he's an extremely good treasurer," Ms Berejiklian said, adding she did not know of any similar staffing arrangements in her office.

"Those arrangements were made directly between the treasurer's office and icare. As to how appropriate or otherwise they were, obviously those requirements weren't taken, which is why the chief of staff of that office's resignation was accepted."

The statutory review is headed by former NSW Supreme Court judge Robert McDougall QC.

icare is an employer-funded workers' insurer, owned by the state but independent from government. It was one of three organisations that replaced WorkCover in 2015.

Australian Associated Press