Nationals' leader Barnaby Joyce and deputy leader Fiona Nash were both disqualified from parliament last week by the High Court because of their dual citizenships. It forced the government to call a by-election in Mr Joyce's New England electorate in northern New South Wales which, having renounced his New Zealand citizenship, he is contesting and expected to win.
But in the meantime, the Opposition has sought legal advice about the validity of decisions Mr Joyce and Ms Nash made while in office.
According to the advice Labor received, any decision made by the pair after October 20th last year may be open to legal challenge.
It means Mr Joyce's decision to relocate a large government department from Canberra to his regional electorate, as well as elements of the National Broadband Network rollout and government appointments, could be vulnerable.

The front entrance of Parliament House in Canberra. Source: AAP
But, now on the campaign trail, the former Deputy Prime Minister and Nationals Leader reminded the Liberals that hisparty played a major role in the Coalition's 2016 election victory.The by-election for Barnaby Joyce's seat is on December the 2nd.