Australia's second most senior law officer says Attorney-General George Brandis's "radical change" to his role is unlawful and threatens his independence.
Solicitor-General Justin Gleeson says he wasn't told about the new legal services direction which rules no one in government, including the prime minister, could seek his advice without the attorney's permission.
Mr Gleeson described it as a "radical change in practice" after 100 years of the solicitor-general's position having existed.
"Do I lie awake at night and think, reading this direction literally, the attorney-general could seek an injunction against me to restrain me performing my office? I do," he told an often heated senate inquiry on Friday.
But Senator Brandis rejected claims he was undermining the solicitor-general.
"Far from being a grab for power, it merely gives effect to existing law," Senator Brandis told the inquiry.
Mr Gleeson said he had not seen the new direction until May 4, after it was issued by Senator Brandis, and said "the more and more I studied it ... was an unlawful direction."
"The change was introduced without the attorney-general telling me about it," he told the inquiry.
"The change is one which is making the function of my office exceptionally difficult."
Mr Gleeson said he had asked Senator Brandis to withdraw the order - which amounted to a "threat" to his office - and engage in proper consultation.
But Senator Brandis says the dispute is a minor "housekeeping" matter which could be resolved in minutes.
He said he consulted Mr Gleeson on November 30 last year on the "substance" but not the form of the legal services direction, which the attorney-general described as a "mere formality".
The attorney's office had sought a meeting with the solicitor-general in April but was informed he would not be available for six weeks.
Senator Brandis said Mr Gleeson had not responded to a further request to discuss the issue in August.
"Had the solicitor-general sought to engage with me ... this issue could have been sorted out in a matter of minutes and at no cost to the taxpayer," Senator Brandis said, adding that he respected Mr Gleeson's independence.
Prime Minister Malcolm Turnbull is confident the stoush between the attorney-general and the solicitor-general will be resolved eventually.
"They support each other," he told reporters in Canberra as the hearing got under way.
"I am sure whatever differences or misunderstandings will be resolved."
Mr Gleeson, in answer to a question from Liberal senator Ian Macdonald, said he had spoken about the issue to shadow attorney-general Mark Dreyfus in June while the government was in caretaker mode during the election campaign.
Mr Gleeson said he wanted to ensure Senator Brandis' statement to parliament, in which he said Mr Gleeson had been consulted, did not go without correction.
Senator Brandis said he had been unaware of the Gleeson-Dreyfus conversation until Friday and had been "shocked" to hear of it.
Coalition senator Barry O'Sullivan questioned why Mr Gleeson had not told Senator Brandis of his conversation with Mr Dreyfus.
Mr Gleeson told the hearing he thought the right thing to do was honestly answer Mr Dreyfus' questions.
Mr Dreyfus said Senator Brandis had misled parliament and should resign.
"Everyone in Australia should be concerned by the grab for power we are seeing from this very destructive attorney-general," he told reporters in Canberra.
