The Liberal MP under the darkest cloud over his citizenship status, Jason Falinski, has for the first time produced legal advice he says puts him in the clear.
Mr Falinski is a first-term MP who last year replaced Bronwyn Bishop in the blue ribbon Liberal seat of Mackellar on Sydney's northern beaches.
Mr Falinski has said he was never entitled to Polish citizenship as his father was never Polish, having been born in the former USSR before becoming a naturalised Australian in 1966.
Legal advice released to Fairfax Media on Wednesday states Mr Falinski would not be considered Polish based on known facts and recollections.
However, several caveats have kept a cloud over Mr Falinski, with Labor intent on having his case referred to the High Court.
Lawyers at Arnold Bloch Leibler conceded they "cannot conclusively advise on foreign law and recommend that you seek independent advice from foreign law experts", which Mr Falinski has not done.
He told Fairfax Media he had received informal advice from lawyers that "over time, yeah, to satisfy any doubt you should do that, but honestly where things stand at the moment there isn't any doubt".
The lawyers also noted it was "unclear to us" whether Mr Falinski's father and paternal grandmother ever acquired Polish citizenship, though they accepted there was no evidence that they did.
The legal letter pointed out under Polish law, Mr Falinski's father would not have inherited Polish citizenship by birth because he was born to unmarried parents.
Furthermore, he would have automatically renounced any citizenship of the USSR when he became a naturalised Australian in 1966. Lawyers also advised Mr Falinski is not eligible for British citizenship.
A confident Mr Falinski told Fairfax Media: "There doesn't seem to be anything where it's open to interpretation. It's a pretty solid piece of advice."
However, that has not satiated Labor, which attempted to refer Mr Falinski's case to the High Court, alongside others.
"That is not solid proof. Upon that you do not base an argument of constitutional eligibility," Opposition Leader Bill Shorten said of the legal advice.
"If that's the best that somebody can put forward, we've got enough doubt that it must go to the High Court of Australia," Labor frontbencher Tony Burke said.
However, Labor MPs were divided over referring Mr Falinski's case because his paternal grandfather, who was born in Krakow, fled the Nazis in 1939.
Labor MP Ed Husic told Sky News some of the citizenship cases were "tit for tat" and reflected the "delightfully feral state of Australian politics right now".
Mr Falinski told Fairfax Media that because of the circumstances of his ancestors' birth, some of the documents his critics were demanding "don't exist".
He also dismissed a ship manifest showing his father declared his nationality as "Polish" when he arrived in Australia - which does not prove Polish citizenship.