Deputy Greens leader Larissa Waters has resigned from the Senate after realising she has been ineligible to sit in Federal Parliament since 2011.
Senator Waters was born in Canada and did not renounce her dual citizenship when running for office, making her ineligible to serve.
The Queensland senator's resignation comes less than a week after Scott Ludlam quit after realising he also held dual New Zealand citizenship.
Both avoidable resignations mean the Greens have lost two of their strongest performers in Parliament in less than a week.
The constitution disqualifies potential candidates from election if they hold dual or plural citizenship.
More to come.