Scott Ludlam, the 47-year-old deputy leader of the minor Greens party, said he was "personally devastated" to learn that he was a citizen of New Zealand as well as Australia, which made him ineligible for the Senate job he has held since July 2008.
The constitution states that a "citizen of a foreign power" is not eligible to be elected to the Australian Parliament.
While lawmakers have discovered they were technically ineligible after elections in the past, Ludlam said nine years later seemed to be a record.
Born in in Palmerston North in New Zealand, Ludlam moved to Perth, Australia, when was 3 years old. He became an Australian as a teenager and said he hadn't realized that New Zealand citizenship "might be something that sticks to you in that way."
Also Read
He was elected to the Senate three times after stating in nomination forms on each occasion that he was not a dual citizen.
He joked: "I can at least vote in the New Zealand elections in September."
Rod Culleton was constitutionally excluded by an undeclared criminal conviction and Bob Day breached the constitution through his financial interest in the building where his senate office was leased.
"I'm hoping common sense prevails," Ludlam said of the prospect of having to repay the government. "If I'd known all along this was the case and I'd just been sprung, maybe they would have a case, but this is as much of a surprise to me as it was to anybody else.
Disclaimer: No Business Standard Journalist was involved in creation of this content