Nationals leader Barnaby Joyce has been forced to a byelection, the government has lost its one-seat majority, and two now-former senators must fight their way back into Parliament, after the High Court disqualified five of the so-called citizenship seven for being dual citizens.

In a judgment handed down Friday afternoon, the court disqualified Mr Joyce the Nationals Leader, Nationals deputy leader Fiona Nash, One Nation senator Malcolm Roberts, and former Greens senators Larissa Waters and Scott Ludlam.