An inquiry must clear new Premier Nathan Rees over whether he knew about disgraced former Labor minister Milton Orkopoulos' crimes before they were made public, the NSW Opposition says.
Before entering parliament, Mr Rees was chief of staff to Orkopoulos, who is serving a nine year prison term after being convicted of child sex and drug offences.
"To date, Nathan Rees' explanation about his role in the Milton affair has been brief at best," Nationals leader Andrew Stoner said in a statement.
"The sum total of Nathan Rees' explanation on the Milton saga has been a two paragraph, 150 word statement.
"There are just too many unanswered questions."
Asked about what he knew - and when he knew it - during his first press conference as premier, Mr Rees said he had no suspicions when he worked for Orkopoulos.
"As I've said before, I found out on the same day as the rest of Australia and I've said that repeatedly," he told reporters.
The coalition had been calling for an inquiry long before Nathan Rees' promotion to premier, Mr Stoner said.
He said it was a matter of character, integrity and judgment and must be resolved.
"What we are asking of Nathan Rees is the same that would be expected of any person taking a senior appointment, whether in private or public life," Mr Stoner said.
"The public must have confidence they have a premier of the highest character."