Labor has asked the Turnbull government to publicly release a list of in-doubt decisions made by two disqualified ministers.
Acting prime minister Julie Bishop says the attorney-general is examining a "few decisions" made by Nationals MPs Barnaby Joyce and Fiona Nash, who the High Court has found to be disqualified from parliament due to their dual citizenship.
Labor has advice from two barristers that the ministers' decisions made since October 20 last year could be open to challenge under section 64 of the constitution.
"I ask that you immediately make public the list of potentially invalid decisions the attorney-general is now considering," Labor senator Penny Wong wrote in her letter to Ms Bishop.
"I also ask you to commit to making the advice the government receives about the legal status of ministerial actions purportedly taken by Mr Joyce and Ms Nash public, including any decisions made by Mr Joyce when he was minister for Resources and Northern Australia."
The federal opposition says the prime minister was "reckless" to allow the two ministers to remain in cabinet while their eligibility for parliament was in doubt.
Mr Joyce, who faces a by-election on December 2, has since conceded he long believed the court might disqualify him, despite the prime minister insisting the court would rule against disqualification.
The South Australian government is seeking legal advice on the status of some of Mr Joyce's decisions, especially in relation to the Murray Darling Basin Plan.