After Greens senator Scott Ludlam was forced to resign last week following citizenship issues, a fellow politician has now followed suit.
Larissa Waters - another Greens senator - has also stepped down from her role in Parliament due to her dual citizenship with Canada.
Under section 44 of the Australian Constitution, persons with dual citizenship are "not permitted to stand for election and that a person must take 'reasonable steps' to renounce their citizenship of the other country."
Waters has been an Australian Senator since 2011 representing Queensland and was the deputy leader of the Greens.
She was born in Winnipeg, Canada before moving to Australia.
In a statement she said, "It is with great shock and sadness that I have discovered that I hold dual citizenship of Australia and Canada. As people would know after the recent departure of my dear friend and former colleague Scott Ludlam, section 44 of the Australian constitution means I cannot hold office in the federal Parliament.
"I left Canada as a baby, born to Australian parents studying and working briefly in Canada before they returned home. I have lived my life thinking that as a baby I was naturalised to be Australian and only Australian, and my parents told me that I had until age 21 to actively seek Canadian citizenship. At 21, I chose not to seek dual citizenship, and I have never even visited Canada since leaving at 11 months old.
"However after Scott’s shock discovery, I immediately sought legal advice, and was devastated to learn that because of 70 year old Canadian laws I had been a dual citizen from birth, and that Canadian law changed a week after I was born and required me to have actively renounced Canadian citizenship.
"I had not renounced since I was unaware that I was a dual citizen. Obviously this is something that I should have sought advice on when I first nominated for the Senate in 2007, and I take full responsibility for this grave mistake and oversight. I am deeply sorry for the impact that it will have.
"It is with a heavy heart that I am forced to resign as Senator for Queensland and Co-Deputy Leader of the Australian Greens, effective today."