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Prime Minister Tony Abbott personally signed off on providing confidential Labor government cabinet documents to the royal commission into the botched home insulation scheme.

Under a long-standing Westminster convention, cabinet documents remain confidential for up to 30 years - a time frame that is being wound back to 20 years by 2022.

But a Senate estimates hearing on Monday was told a lever arch file of confidential Labor government cabinet documents had been provided to the royal commission, with the approval of Mr Abbott.

Department of Prime Minister and Cabinet deputy secretary Elizabeth Kelly told the hearing the government had received a broad summons from the royal commission for any documents relating to the insulation scheme.

A search of the department's records found 4500 documents, which were passed on in late January to the royal commission via the attorney-general's department.

Cabinet documents were passed on to the inquiry a week later, accompanied by a letter setting out the conditions under which they could be used.

Asked who made the decision, Ms Kelly said: "The department has implemented a decision made by the prime minister."

Ms Kelly said the government could still exercise public interest immunity rights over the documents if necessary, which would prevent their use by the commission.

She said not complying with the summons could result in criminal sanctions.

Veteran Labor senator John Faulkner said the decision had breached the cabinet handbook, which stipulated that cabinet records were held under the care and control of the secretary of the department, not the prime minister.

The handbook also made it clear cabinet documents were confidential to the government that created them.

"It's an open and shut case of a breach of literally what is now 113 years of government and cabinet practice and convention," Senator Faulkner said.

Liberal frontbencher Eric Abetz told the hearing the royal commission's summons had "greater power and authority" than the cabinet handbook.

Senator Abetz said that cabinet documents had been provided to at least two previous judicial inquiries, including the probe into the detention of Dr Mohammed Haneef.

"So let's not talk about this 113 years of precedent," the minister said.

Senator Faulkner said that in the Haneef case, the commission agreed to discuss the cabinet papers only with former ministers or ex-officials and other strict conditions applied.

Labor says the royal commission is a political witch hunt, but the government argues the public has a right to know more about how four insulation scheme workers died and why the Rudd government did not put greater checks in place and heed industry warnings about its dangers.