It seems a long time ago that a bunch of political fringe-dwellers were demanding on social media that Prime Minister Tony Abbott prove he’d renounced his British citizenship. It was an annoyance for him then, but it may be an unexpected bonus now.

The anti-Abbott campaigners were dubbed “birthers” after the US controversy around Barack Obama’s birthplace and similarly dismissed as desperate nutters.

This week no one is smirking at the conspiracists after the dual citizenship revelations saw the Greens lose two senators and the government’s majority cast into doubt.

The Abbott-birthers were dismissed on the assumption political parties were professional outfits that would ensure their candidates did not fall foul of section 44 of the Constitution, which lists the ways in which someone can be ineligible.

It’s not as if the issue hadn’t been raised before. The ABC’s election analyst Antony Green had noted that in 1992 the High Court ruled two foreign-born Australians were ineligible to be candidates in the previous federal election because they had not rid themselves of “any acknowledgment of allegiance, obedience, or adherence to a foreign power” or taken all “reasonable steps” to do so.

Yet only four years later, Liberal MP Jackie Kelly was disqualified from parliament for not having renounced her New Zealand citizenship (and also for not having resigned from the RAAF), prompting the Howard government to call a parliamentary inquiry into the troublesome section of the Constitution.

Granted, this occurred 20 years ago. Maybe that goes some way to excusing the newer parties, but it would be reasonable to expect the major political parties are more professional than they were then – with even more rigorous candidate selection processes.

The Labor Party’s national secretariat issued a statement after the Greens lost two senators to section 44, assuring the media that it “works closely with all our candidates to ensure that their nomination is sound and compliant with the Constitution”, and that it was “confident that every member of the Labor caucus has been properly elected.”

That was before this week’s revelation by Turnbull government minister Matt Canavan exposed one of the apparently numerous ways an Australian MP with foreign heritage could unwittingly become a dual citizen. Now Labor has gone quiet, no doubt while the credentials of its MPs are double-checked. Unlike Labor, the Liberal Party chose not to lead with its chin, which was lucky given two of its MPs were under a dual citizenship cloud by the end of the week.

Usually in such potential cases of mutually assured destruction, Labor and the Coalition call an unofficial ceasefire, with each party holding off attacks on the other in the hope of minimising their own damage. However, minor party and independent MPs are fair game, as we saw with Labor’s legal challenge to the eligibility of Kenyan-born independent senator Lucy Gichuhi. If Labor’s house is in order, the temptation to wound the Turnbull government by bringing down one of its MPs might be too hard to resist.

This will particularly be the case if the parliamentarian sits in the House of Representatives, where the Coalition has a majority of one. The speculation on Friday was that the unfortunate MP might well be Australian-born Julia Banks, who it was said might have acquired Greek citizenship courtesy of her Greek-born father. A statement from the Greek embassy saying Ms Banks is not a citizen and never had been removed much of the heat from the flap.

Losing a lower house MP would not bring down the Turnbull government, given the three independents Bob Katter, Cathy McGowan and Andrew Wilkie have all agreed to back the government against any no-confidence motion. However a by-election would have to be held to fill the vacancy created by the departure of any ineligible MP. And given the current state of the polls, this could turn out to be a very ugly – and potentially fatal – referendum on the performance of Malcolm Turnbull.

This would play right into the hands of the man who inspired the renaissance of “birtherism” in Australia. Instead of removing him from office, the politically-driven witch-hunt for undeclared dual citizens could create the crisis Tony Abbott needs to bring down the prime minister and return to the leadership.

For if there’s one foreign-born MP who seems to be in the clear on section 44, it’s Mr Abbott. During his tenure as PM, Mr Abbott and his advisers strenuously resisted all attempts to make his renunciation of dual citizenship public.

This month, as soon as the first Greens senator resigned, the former PM tweeted an image of the document, saying “FYI rumour mongers, I renounced my UK citizenship in 1993 and here’s the proof”.