GREENS leader Richard Di Natale is racing to produce proof he has properly renounced his Italian citizenship after two of his deputies were forced to resign after failing to conduct sufficient checks.

Earlier this week deputy Greens leader Larissa Waters quit parliament over a citizenship issue today, just days after Scott Ludlam also resigned for the same reason.

Waters was born in Canada, but moved to Australia at a young age. She still holds dual citizenship with Canada.

Under the Australian Constitution a ­person who is a foreign national cannot be elected.

Senator Di Natale’s office has said he renounced his citizenship a decade ago prior to his election to parliament in 2010.

The Australian reports Di Natale’s office says he renounced his citizenships ‘over a decade ago’. Senator Nick McKim says he gave up his UK citizenship in 2015 before taking up a position with the Greens after the departure of Christine Milne.

“Both Senator Richard Di ­Natale and Senator Nick McKim renounced their citizenship before they stood for election and can provide documentary evidence when they receive it from the appropriate officials,” a Greens spokeswoman said.

Meanwhile, the Greens leader believes two of his former senators shouldn’t have to pay back their parliamentary salaries despite being ineligible to have served.

Di Natale has ordered a root-and-branch review of the party’s processes and insists the party vets all its candidates and both indicated they weren’t dual citizens.

“We should have triple-checked and we didn’t,” he told ABC radio.

The rest of the Greens party — including Singaporean-born Peter Whish-Wilson and Nick McKim, who was born in the UK — have checked their citizenship status.

Senator Di Natale doesn’t believe Ms Waters and Mr Ludlam should have to pay back their salaries or be treated differently to former senator Bob Day, whose debt was waived.

“They’ve already paid a pretty high price,” he said.

Former prime minister Tony Abbott, who has released a letter showing he renounced his British citizenship in October 1993, says the law has been clear for many years and there are “no excuses”.

“It is part of the constitution and frankly, if we were going to change the constitution, this wouldn’t be my first priority,” he told 2GB. Immigration Minister Peter Dutton had more sympathy for the senators, acknowledging the sad circumstances.

“Whilst I might disagree with their politics vehemently, I can understand at a personal level they made a mistake,” he told ABC radio.

Labor leader Bill Shorten said while he felt for the two senators, Australians would be right to question what was going on with the Greens. “Are they ready to be serious political operators? Are they up for the job?” he asked reporters in Sydney.