Queensland Greens senator Larissa Waters has followed Western Australian colleague and co-deputy leader Scott Ludlam out of the Senate this afternoon, revealing she was unaware that she had Canadian citizenship and thus had also fallen foul of section 44 of the constitution.

According to a statement by Waters, she was born in Canada while her Australian parents were briefly living there and left as an 11-month old, but this was sufficient to give her Canadian citizenship despite subsequent legal changes in Canada that would have prevented that. On Friday, Scott Ludlam revealed he had learnt he had retained New Zealand citizenship despite leaving the country as a child and being naturalised as an Australian. 

Waters was elected in the 2010 election, which was the first time the Greens secured a Queensland senator. She retained her spot at the 2016 election.

The dual resignations have focused attention on the poor internal processes of the Greens state parties, which have failed to perform basic checks on candidates. Ludlam’s citizenship issue has been overlooked since 2006; like Ludlam, Waters will technically be required to repay her salary and entitlements since 2010, but she might appeal to avoid the obligation, as former senators Day and Culleton have in recent months.

Former senator and Australian Democrats leader Andrew Bartlett was second on the Greens ticket in Queensland in 2016 behind Waters and is likely to replace her. Bartlett was last in the Senate in 2008, having lost his spot in the 2007 election.

The second citizenship-based resignation in a matter of days has sharpened focus on a number of overseas-born senators and members, who may fall foul of the section 44 requirement that candidates for Parliament not owe any allegiance to a foreign power (even the Queen, in the case of Ludlam and Waters). Tony Abbott, Mathias Cormann and One Nation’s Malcolm Roberts have all stated they have renounced or lost non-Australian citizenships.