Australia's prime minister said Monday that he was confident that government lawmakers would win a court challenge this week that threatens his administration's slender majority.

Seven High Court judges will decide whether seven lawmakers should be disqualified from Parliament because of a constitutional ban on dual citizens being elected. The three-day hearing begins Tuesday.

The fate of Deputy Prime Minister Barnaby Joyce is most crucial to the government in an unprecedented political crisis.

If the court rules that he was illegally elected in July last year due to New Zealand citizenship he unknowingly inherited from his father, the ruling conservative coalition could lose its single-seat majority in the House of Representatives, where governments are formed.

Joyce could stand in a by-election, having renounced his Kiwi citizenship. But with the government unpopular in opinion polls, voters in his rural electoral division could take the opportunity to throw both the deputy prime minister and his administration out of office.

Two of the six senators under a cloud are government ministers. Fiona Nash inherited British citizenship from her father and Matt Canavan became an Italian through an Australian-born mother with Italian parents. Disqualified senators can be replaced by members of the same party without need for an election.

Prime Minister Malcolm Turnbull has given no indication of what his government would do if the court rules against any of the three ministers.