Attorney-General George Brandis outlined the plan to make cabinet documents available in a letter to his predecessor, Mark Dreyfus, who says it turns 113 years of established practice on its head.

Former prime ministers Bob Hawke and Malcolm Fraser have expressed alarm at the move, saying it will invite payback from future governments and threaten cabinet confidentiality.

Lawyers representing former prime ministers Kevin Rudd and Julia Gillard and several former cabinet ministers who have been summoned to appear before the commission are believed to be considering legal action that would see the courts decide if cabinet confidentiality should be waived in the public interest.

Four men died while installing home insulation under the $2.5 billion scheme, which was rolled out as a stimulus measure at the height of the global financial crisis. There were also fires in hundreds of homes.

''If you are going to start the practice in which the new incoming government has royal commissions chasing its predecessor, then there'll be payback and the next incoming government will do it, too - and you can ultimately make democracy as we know it, and understand it, unworkable,'' Mr Fraser said.

Mr Hawke said it was ''almost beyond belief that the government could contemplate doing anything which breaches what is now a more than century-old tradition here, which has been respected by governments and parties of both persuasions''.

A spokesman for Senator Brandis would not confirm when, or if, cabinet documents had been handed to the commission, in which Ian Hanger, QC, will examine the process under which the program was established and implemented.

It will also investigate if the deaths of the four could have been avoided ''if the Australian government had taken a different approach to identifying, assessing or managing workplace health and safety risk''.

Senator Brandis said the government respected the importance of cabinet confidentiality, but it had decided the documents the Commonwealth would produce for the commission ''will include documents over which a claim for public interest immunity might be made, such as cabinet documents''.

In providing such documents to the commission, Senator Brandis said the government would indicate that it did not waive its right to claim public interest immunity from their contents becoming public.

''Accordingly, should the commission wish to publish any of the cabinet documents … the Commonwealth requests that it be notified so that it can consider whether it is necessary to make submissions in relation to such documents or uses, or whether it should seek protective orders,'' he said.

Mr Abbott has strongly denied that the royal commission is an exercise in payback.