Turnbull government MP Nola Marino may have acquired Italian citizenship through marriage, in what would represent a new twist in the eligibility crisis that has engulfed the federal Parliament.
Ms Marino's case also highlights a gap in the proposed new disclosure regime being debated by Prime Minister Malcolm Turnbull and Opposition Leader Bill Shorten, which does not consider the possibility of dual citizenship attained through marriage.
The development comes after fellow Liberal MP John Alexander declared he was still waiting on "conclusive" advice from the UK Home Office about his citizenship status. There is mounting speculation he will resign by Monday, sparking a byelection in his Sydney seat of Bennelong.
Also on Friday the High Court decided to examine the eligibility of Hollie Hughes, the Liberal who was set to replace former deputy Nationals leader Fiona Nash. Ms Hughes is under a cloud because after last year's election she took up a government job, which could disqualify her from office .
The citizenship spotlight has now fallen on Ms Marino, who married her husband, Carmelo Marino, in Western Australia in 1972.
Mr Marino - who goes by the name Charlie - was born in Italy in 1950 and emigrated to Australia with his parents the following year, according to ancestry documents seen by Fairfax Media.
That means Mr Marino was an Italian citizen at birth. If Mr Marino naturalised as an Australian before 1972 he would have lost his Italian citizenship and not passed it on to Ms Marino.
But if he retained it she too would have become an Italian citizen.
Official Italian government advice clearly states: "Foreign women who married an Italian citizen prior to 27 April 1983 automatically acquired Italian citizenship on the date of marriage."
Ms Marino, who as the Chief Government Whip in the House of Representatives is responsible for party discipline, has so far failed to clarify the facts around her situation, refusing to say whether she or her husband ever relinquished Italian citizenship.
While people who marry Italians now must go through a long naturalisation process to become citizens, the official Italian government advice emphasises that for people in Ms Marino's situation there is "no need" to naturalise or activate.
There is a "recognition" process for people in Ms Marino's situation, this is not considered a prerequisite to citizenship.
Italian immigration and citizenship expert Sara Bucalossi, who works with leading consultancy Mazzeschi, confirmed that unless Mr Marino relinquished his citizenship, he would have passed it on to Ms Marino.
"This means that Nola could request the recognition of her Italian citizenship," Ms Bucalossi said.
Ms Marino and her office declined to answer a detailed series of questions put by Fairfax Media, but in a statement said: "I am an Australian citizen and only an Australian citizen."
"The High Court made clear that Italian law requires the taking of the positive steps to acquire citizenship. I have never taken such steps," she said.
In considering the case of Turnbull government cabinet minister Matt Canavan last month, the High Court found it could not be "satisfied" he was a citizen of Italy, in part because he took no positive steps to attain the status.
But Senator Canavan's case related specifically to Italy's notoriously complex system of indefinite "jus sanguinis" citizenship by descent. Ms Marino's case relates to a different - and more straightforward - area of Italian law.
And section 44 of the Australian constitution makes no distinction between different forms of citizenship, meaning if Ms Marino was found to be an Italian citizen through marriage she would be ruled ineligible.
That would force the government into another byelection, although Ms Marino's WA seat of Forrest is safe Liberal territory. She has held it since 2007 and her current margin is a comfortable 13.8 per cent.
Ms Marino's name has not previously been mentioned amid the dual citizenship fiasco that has so far seen five MPs removed from Parliament and threatens the future of many more.
Ms Marino was herself born into a family with Italian heritage in 1954, as the daughter of Sam and Alma Catalano.
Ms Marino has never named her own family in Parliament, but local history records show her father, Sam, was born in New York in 1920.
Fairfax Media does not believe Ms Marino could have automatically acquired US citizenship through her father due to the complex laws in place between 1952 and 1986.
Ms Marino is a close ally of Mr Turnbull, who has previously described her as a "legend". She was promoted after the ousting of Tony Abbott from the prime ministership, becoming the fist woman to hold the office of chief government whip.
