Mr Perrottet provided the figures at a budget estimates sitting on Monday when quizzed about the pace of the review and curious payments to a labour hire company.

The review has so far cost the insurer $3.5 million, with $260,000 issued to the 24 workers.

It was initiated after the underpayments to possibly tens of thousands of injured workers were exposed almost a year ago.

The treasurer acknowledged the slow progress was of "concern".

"I accept ... that this has taken too long," he said. "This is something that needs to be resolved."

Mr Perrottet was also quizzed about tens of millions of dollars paid to a labour hire company, which also appears to lease several floors of icare's Sydney office building.

The NSW government's tender database shows icare agreed to pay Comensura Pty Ltd over $235 million in two separate contracts over four years between 2017 and 2021. One contract includes office leasing costs.

Greens MP David Shoebridge also produced a document showing three levels of icare's building on Kent Street in Sydney are leased to Comensura.

But icare occupies two of those levels, icare chief executive Richard Harding told the committee.

Mr Harding said he was not aware that office space was being leased by Comensura but occupied by icare.

Labor MP Daniel Mookhey said the documents showed icare had paid for fit-out and labour costs at icare's Kent Street premises.

"Why are we paying ... to lease an office with waterside views for a labour hire company?" Mr Mookhey asked Mr Perrotet.

The treasurer said he was not familiar with the arrangements but agreed it "intuitively" raised concerns.

The contracts were initially not published on the govermnent's eTendering website, which drew criticism from the NSW auditor-general in December.

The auditor-general criticised icare for failing to comply with legal requirements to disclose contracts in a report, saying 417 had been missing from the 2019-2020 financial year.

The report identified the Comensura contracts as significant procurements that had not been procured.

The treasurer again apologised to anyone who had been "adversely affected" by icare's shortcomings.

He also defended the salary of icare's new CEO, Richard Harding, who is paid more than $820,000 plus a potential bonus.

Mr Perrottet refused to rule out an electric vehicle levy or tax, which has been controversial in Victoria.

"If you use roads you should pay for them ... but we don't want a tax that's going to be an impediment to take up an innovation."

He trumpeted his government's response to the COVID-19 pandemic but said he was concerned international students were still not entering the state.

Australian Associated Press