Greens senator Larissa Waters resigned on Tuesday after revealing she also held Canadian citizenship, days after her party colleague Scott Ludlam was forced to step down after discovering he held dual citizenship with New Zealand.
Australia’s constitution bars dual citizens from eligibility for elected office, unless they can show they have taken reasonable steps to sever foreign ties. Although Ludlam served in the upper house for nine years and Waters for six, the revelations mean they were technically never senators.
A visibly emotional Waters apologised for failing to conduct the necessary checks to ensure she was eligible to sit in parliament.
She said she had learned with “shock and sadness” she was a dual citizen after checking last week.
“I had not renounced since I was unaware that I was a dual citizen,” she said. “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.”
Waters was known for her environmental advocacy, including campaigns to save the Great Barrier Reef, which is under significant threat from the effects of climate change. She also made headlines around the world for becoming the first woman to breastfeed in Australia’s parliament.
Ludlam, who moved from New Zealand to Australia when he was three years old, said the mistake over his citizenship was an “avoidable oversight” that was “entirely [his] responsibility”.
The Greens leader, Richard Di Natale, acknowledged his party had chalked up a “terrible month”.
The departure of two of the Greens’ nine senators follows recent high court proceedings against two other senators, Bob Day, who represented the conservative Family First party, and Rod Culleton, another rightwing independent, after both offended constitutional provisions.
The recent run of Senate resignations is unprecedented in Australian politics.
The departure of the two Greens means the party’s presence will be reduced in Australia’s finely balanced upper house until their replacements are sworn in, a development that could enhance the ability of Australia’s centre-right Coalition government to pass contested legislation.
The federal government, led by Malcolm Turnbull, governs with a wafer-thin one-seat majority in the lower house, the House of Representatives, and does not command a majority in the Senate.
While Turnbull has been considerably more successful than his predecessor, Tony Abbott, in navigating government legislation successfully through the Senate, the government has so far not been able to persuade the upper house to pass a contentious bill that would deregulate media ownership.
Australia has one of the most concentrated media markets in the developed world, with Rupert Murdoch’s News Corporation a dominant print player. The government’s blocked legislative proposal would benefit incumbent media moguls, like Murdoch, by making it easier for them to merge with or acquire their competitors and expand their news operations across platforms.
On Tuesday, critical members of Australia’s upper house – the leaders of the South Australia-based Nick Xenophon Team, and the rightwing One Nation party – warned Turnbull against exploiting their temporary advantage.
It later emerged that the Turnbull government had agreed to “pair” the two Greens senators until their replacements were sworn in. The pairing convention between opposing parties requires abstentions from votes to maintain the numerical balance of the chamber.
The Greens have been plagued by factional infighting triggered by a schools funding debate and have now been hit by the loss of two high-profile senators who are also allies of the party leader.
Di Natale said he had taken steps to ensure the administrative oversights by Ludlam and Waters were not repeated with future Greens candidates.
“There is no question here – I won’t sugarcoat it – we need to make sure that our internal party processes are up to the challenge,” Di Natale said.
“We have to improve our governance. We have to strengthen our internal processes and we have to make sure that this doesn’t happen again.”