Senator Waters said it was with "great shock and sadness" that she made the discovery she was still a citizen of the country she had not visited since she was 11 months old. Greens senator Larissa Waters was forced to resign after discovering she was also a Canadian citizen. Credit:AAP In an emotional press conference in Brisbane on Tuesday, Senator Waters said she was "devastated to discover" if she had been born a week later, she would not be in this position. Senator Waters said she had lawyers look over her status over the weekend, following her colleague's discovery, and learnt late Monday afternoon she held dual-citizenship. "I left Canada as a baby, born to Australian parents studying and working briefly in Canada before they returned home," she said.

"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. Scott Ludlam (right) and Larissa Waters (left) served as co-deputies to Greens leader Richard Di Natale. Credit:Andrew Meares "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. The Greens have been rocked by a second resignation after Queensland Senator Larissa Waters quit upon realising she, too, was a dual national. Credit:Alex Ellinghausen

"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. "I apologise wholeheartedly to all those who have supported me and helped me to become a representative for the wonderful people of Queensland over the last six years." Senator Waters became the second Greens senator in less than a week to step down because of the constitutional oversight, with Senator Ludlam stepping down on Friday after a decade in the red chamber, after discovering he was still a New Zealand citizen. Greens leader Richard Di Natale said he was "gutted" by the announcement. "This is unprecedented and deeply disappointing – personally for Larissa, for her family and for the Greens federally and in Queensland," he said in a statement.

"The Parliament and the nation are worse off as a result of the resignation of two leaders of such integrity and ability as Larissa and Scott. "This is an innocent mistake, and Larissa has acted quickly and honestly to correct it. I commend her for that. She's paid a very high price for this error." Senator Di Natale said he had spoken to party convenors and committed to an urgent review of processes. "As our party grows, we need to strengthen our governance and internal processes including how we vet candidates to prevent this from happening again," he said. "...Let me say this to our Greens family – my colleagues, our members, supporters and voters: today's news is challenging, but we are a movement founded in our solidarity and our commitment to working together to deliver change and to offer people choice in how we live our lives and make the world a better place for coming generations."

Senator Waters said she will talk with her party, which has been thrown into chaos with the loss of two of its most experienced performers in a matter of days, about her future, but remains proud of her achievements, which include becoming the first woman to breastfeed in Federal Parliament and working to maintain key environmental protections. "It has been an honour to work with my Greens colleagues in the Parliament and in the Queensland party," she said. "They are the best of people and I am devastated to leave them. My focus now is on working with the party to ensure Queenslanders still have a strong Green voice in the Senate, and working with our state candidates, members and supporters to elect Greens into the Queensland State Parliament. "Despite my personal circumstances, I still have unshakeable hope for our common future on this planet. "Our movement is so much bigger than any one person, and we will win in the end. Farewell dear friends."

Senator Waters said while it was "my job to check", the Greens would review their selection processes. But she said it was "way bigger than one person". Mr Bartlett, who has served as the Queensland Greens Party Convenor for the past few years after losing his senate spot in 2007, is expected to be named the successor following a count back of votes. He was widely expected to join Senator Waters in the Senate in the lead up to the 2016 election, with the Greens having made strong inroads in Queensland over the past few years. Parliament has had some practice with section 44 resignations in the past few months, with One Nation's Rod Culleton and Family First Bob Day both losing their positions. "My immediate focus is on working with the many thousands of wonderful members and supporters of the Greens in Queensland to work through this situation so that we can continue to present an effective alternative to the establishment parties who fail our community and our environment so badly," he said.

"The party's membership will be having many conversations over the next few days as we process what has happened and determine what is the best way forward to ensure we remain a strong voice for the essential values the Greens promote." Senator Waters is expected to ask for the same waiver given to Mr Day and Mr Culleton, to protect against the Commonwealth pursuing her for funds. Loading Former prime minister Tony Abbott responded to questions from independent senator Derryn Hinch about whether he was a dual citizen on Friday by publishing a document showing he had renounced his British citizenship in 1993.