Remember all those Wildean-gags made at the expense of the Greens after a teary Larissa Waters was forced to resign from the Senate due to her Canadian citizenship? It came just a few days after the Greens' other co-deputy leader, Scott Ludlam, was forced to resign over his New Zealand citizenship, and made the Greens a laughing stock.

Prime Minister Malcolm Turnbull was unsympathetic. "It shows incredible sloppiness on their part," he said of Ludlam. "You know, when you nominate for Parliament, there is actually a question ??? you have got to address that section 44 question and you've got to tick the box and confirm that you are not a citizen of another country."

But it turns out that such carelessness was not isolated to the Greens. It is now clear there has been a widespread failure among candidates to meet the requirements of our constitution.

In the month since the Greens leadership group was smashed by section 44 of the constitution, we've seen Nationals minister Matt Canavan, One Nation's Malcolm Roberts, Nationals leader Barnaby Joyce and his deputy Fiona Nash and now Nick Xenophon, leader of the eponymous centrist party, referred to the High Court.

Who will be next? All of the MPs caught have said they had no no idea they were foreign citizens until recently. But many of those under a cloud have appeared reluctant to produce the paperwork.

In the strange case of Michael Keenan, the Justice Minister refused to answer Fairfax Media's questions about whether he had rescinded his British citizenship status for two days and only did so after the seriousness of those doubts were publicly aired.

Until all federal politicians are independently examined, it is reasonable to expect that more ineligible MPs will emerge.

Greens leader Richard Di Natale warned from the start that more would soon be found. "I think both sides of politics know people on their own side who [are] going to be caught up in it," ???he told Sky News last month.

Conservatives senator Cory Bernardi claimed this week that staffers are walking the corridors of Parliament House well aware that their MP is not eligible under section 44.

While the government is in crisis over the revelations that have put its grasp on power at risk, Labor has remained unscathed. The Coalition is pressing hard for evidence regarding five Labor MPs - Maria Vamvakinou, Tony Zappia, Justine Keay, Brendan O'Connor and Susan Lamb - and have threatened to refer their cases to the High Court for investigation.

Questions even hover over Opposition Leader Bill Shorten, who says he renounced his dual citizenship in 2006 before entering Parliament but has inexplicably failed to present the evidence.

Labor insists it has thorough processes to ensure its candidates aren't dual citizens, but until the party backs up its claims we are expected to take their word that not one of the party's 95 MPs has made a mistake.

As long as Labor avoids being embroiled, the Turnbull government bears the burden of this constitutional crisis.

But this cloud over the whole Parliament needs to be resolved.

The only solution is for the government and opposition to back an immediate inquiry into whether every MP in the Parliament should truly be there.

What could they possibly have to hide?

Damien Nowicki is producer for Fairfax federal politics coverage.

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