Labor believes more than 100 Turnbull government decisions are vulnerable to legal challenge as a result of Barnaby Joyce and Fiona Nash’s dual citizenship status.
The opposition has received legal advice on a range of decisions which could be challenged after the High Court disqualified Mr Joyce and Ms Nash from parliament.
Among the 118 decisions under threat are ministerial announcements and grants, legislative instruments, water access entitlement payments, elements of the NBN rollout and the mobile black spot program.
Acting Labor Leader Tanya Plibersek said some decisions were likely to have left people feeling aggrieved.
“If they want to pursue the government on some of them, I don’t doubt they will,” Ms Plibersek told ABC radio on Monday.
“No doubt there will be some people who will be wondering whether they were treated fairly and whether decisions were made properly by Fiona Nash and Barnaby Joyce when they weren’t properly elected to the parliament.”
The High Court would be asked to rule on whether the decisions were constitutionally valid, as they were made after the two ministers ceased to hold office last October.
However, Mr Joyce is confident the decisions he took as a minister will stand because his dismissal is not retrospective.
The former deputy prime minister and four senators were found to hold dual citizenship and constitutionally ineligible to nominate for parliament at the 2016 election.
Mr Joyce said when you are declared in an election, you stay that way until you “die, resign or the High Court finds you ineligible”.
“Not the High Court finds you ineligible, therefore retrospectively, it’s when the High Court finds you ineligible,” he told reporters on the campaign trail in his seat of New England on Sunday.
Voters will go to the polls in his seat of New England on December 2.
Mr Joyce is expected to win, but the government will face a rocky time in the interim after losing its one-seat majority, especially when the House of Representatives next sits in the week of November 27.
Independent MP Cathy McGowan and NXT MP Rebekha Sharkie have indicated they will back the government in a no-confidence motion.
But potential votes on a banking royal commission and keeping Sunday penalty rates could yet prove a splintering headache for the Turnbull government.