Australian Deputy PM Barnaby Joyce and four other politicians were wrongly elected because they held dual citizenship, a court has ruled.
The High Court of Australia decision means three of the politicians, including Mr Joyce, are disqualified from office. The others quit in July.
Australia’s constitution prohibits dual citizens from being elected.
Mr Joyce’s exit strips the government of its one-seat majority, but he could return through a by-election.
The deputy prime minister, who renounced New Zealand citizenship in August, has pledged to re-contest his lower house seat.
“I respect the verdict of the court,” Mr Joyce said immediately after the verdict.
“We live in a marvelous democracy, with all the checks and balances they have given us all the freedoms we see. I thank the court [for] their deliberations.”
The other four politicians – Fiona Nash, Malcolm Roberts, Larissa Waters and Scott Ludlam – had been elected to the Senate.
Another two politicians under scrutiny, senators Matt Canavan and Nick Xenophon, were ruled to have been validly elected.
The dual citizenship saga has captivated Australian politics since July, prompting dozens of MPs to publicly clarify their status.
During three days of hearings, the court was told that only Mr Roberts and Mr Ludlam should be disqualified, arguing the others did not know about their dual citizenship when they were elected last year.
Mr Roberts claimed he had tried to revoke his citizenship. Mr Ludlam and Ms Waters, did not offer a defence – arguing all seven should be ineligible.
The seven-judge bench deliberated for two weeks before ruling that five politicians were ineligible as a “subject or citizen of a foreign power”, under to the constitution.
The court ruled that Mr Canavan and Mr Xenophon were not dual citizens, according to the constitutional definition.
The court was not satisfied that Mr Canavan had attained Italian citizenship through descent, while Mr Xenophon’s class of inherited UK citizenship did not give him full rights and privileges.
With Mr Joyce disqualified, Prime Minister Malcolm Turnbull’s numbers slip to 75 in the 150-seat House of Representatives – meaning he is now overseeing a minority government.
However, Mr Turnbull could regain his 76-seat majority if Mr Joyce wins the by-election on 2 December. Mr Joyce is eligible to run now he is a citizen of Australia alone.
Under a minority government, Mr Turnbull will require support from independent MPs and minor parties to pass legislation in the lower house.
He has also reshuffled his cabinet because both Mr Joyce and Ms Nash held ministerial portfolios.
The Labor opposition has claimed that decisions made by the two ministers are “under a legal cloud” and could be challenged.