Australia's Deputy Prime Minister Barnaby Joyce has been removed from parliament for being a New Zealander, putting the government's majority at risk.
The ejection of the Nationals leader means the government will lose its one-seat majority in the House of Representatives and likely embolden Labor, which has threatened to cause chaos and confusion if Mr Joyce's election is deemed invalid.
"I had no reason to believe that, you know, I was a citizen of any other country than Australia".
The court also ruled on the status of six other lawmakers in the Senate.
It tumbled to a 0.8 per cent loss after the court disqualified Deputy Prime Minister Barnaby Joyce, forcing a by-election, but it bounced to close down 13.1 points, or 0.22 per cent, at 5903.2.
The disqualified senators will be replaced by members of their own party without an election, meaning the balance of power will only be affected by Mr. Joyce's situation. Two of them however are government ministers, Fiona Nash who inherited British citizenship from her father and Matt Canavan who became an Italian through his maternal grandparents.More news: UK GDP: Britain's economy grew by 0.4% in the last quarter
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"The decision of the court today is clearly not the outcome we were hoping for but the business of government goes on", Prime Minister Malcolm Turnbull said this afternoon.
Constitutional lawyer Anne Twomey said there may be a legal challenge to any decision Joyce took once questions had been raised about his eligibility.
Three parliamentary investigations recommended in the 1980s and 1990s that the prohibition on dual citizens be removed from the constitution through a national referendum.
Previously only two lawmakers had ever been caught out by the foreign citizen ban, although other dual citizens have nearly certainly served in the Parliament undetected.
The seven lawmakers said they did not know they were dual nationals when they ran for election past year.