Labor has accused the prime minister of being unable to discipline Nationals members on the frontbench, such as former deputy prime minister Barnaby Joyce, because of undertakings made in the secret coalition agreement.

"Is the prime minister powerless to act against a minister who breaches the ministerial standards when that minister is a member of the National Party and there any formal agreements that prevent the prime minister from enforcing his own ministerial standards," Labor leader Bill Shorten asked in parliament.

"The answer to those two questions are no and no," Mr Turnbull said.

"The ministerial standards are enforced and have recently been revised."

Earlier, Labor frontbencher Joel Fitzgibbon called for transparency regarding the coalition arrangement that saw new Nationals leader Michael McCormack elevated to the deputy prime ministership on Monday.

Mr Turnbull told parliament the coalition agreement was an "administrative agreement only" between the Liberal and National parties.

"It has not been made public in the past," he said.

Nationals deputy leader Bridget McKenzie told ABC TV on Sunday it was not a "sacred document" and the governor-general was "across it".

However, Mr Turnbull said the governor-general had only seen a letter from the Nationals leader confirming the government has the support of the Nationals on the floor of parliament, not the text of the agreement.

Mr Fitzgibbon said Australians didn't understand the coalition agreement or why the government was determined to keep it a secret.

He cited Germany and New Zealand as precedents where coalition power-sharing arrangements had been made public.

Mr Fitzgibbon had been engaged in court action for several years to make the coalition agreement documents public.

Legal expenses were paid partly out of his own pocket, as well as crowd-funding and support from the legal firm he had engaged.

"The Australian taxpayer is paying expensive lawyers to keep Malcolm Turnbull's coalition deal secret," he said.

Australian Associated Press