More than 100 ministerial decisions made by the former Nationals leadership team of Barnaby Joyce and Fiona Nash when they were ineligible to be in Parliament are now vulnerable to legal challenges by various vested interests and political opponents.

As the government flagged changes to citizenship laws on Sunday to prevent a repeat of the constitutional fiasco that saw the High Court disqualify five MPs on Friday, the opposition turned its attention to the decisions made by Mr Joyce and Ms Nash who continued to act as ministers despite having a cloud over their validity.