The Opposition is critical of a letter from the Attorney-General to members of a South Australian Parliamentary Select Committee warning them they may break the law by discussing the Debelle royal commission findings.

The Opposition said the letter referred to the Royal Commissions Act of 1917, which banned review or questioning of decisions and proceedings of an inquiry.

It said Attorney-General John Rau sent the letter last week, before the committee held its first hearing to consider issues raised by the Debelle inquiry.

Opposition frontbencher Rob Lucas said the letter was a desperate act by the Government to stifle accountability.

"This committee isn't rehearing or reviewing the Debelle Royal Commission anyway, it's there to look at the unanswered questions that have been raised by the Debelle Royal Commission," he said.

"Last week it was claimed by the Weatherill Government that this committee was unconstitutional and this week that it's contrary to the provisions in the Royal Commission Act.

"If you actually interpreted the Royal Commission Act in the way the Weatherill Government is seeking to do, there'd be a lot of journalists, MPs and committee members already in jail as a result of supposedly breaching past royal commission hearings and findings."

The Attorney-General said it was his responsibility to tell the members of the parliamentary committee of a potential legal risk their hearings could raise.

Mr Rau denied he was making an attempt to stifle debate and accountability.

He said he was simply trying to bring the matter to the committee's attention after his department had informed him.

"I'm just letting them know. I don't know where they want to go, I'm not involved in the inquiry," he said.

"But, having had that information drawn to my attention, I would later be criticised quite reasonably for having not told anybody if somebody wound up in trouble."

SA's Premier and current and former education ministers have refused to face the parliamentary inquiry, which was set up by Opposition members of the upper house.

It stems from school sexual abuse cases and how they were investigated by education authorities in SA.