EMMA ALBERICI, PRESENTER: The dual citizenship farce in Federal Parliament has struck the nation's second highest office with the Deputy Prime Minister, Barnaby Joyce, confirming he is a citizen of New Zealand.

But unlike the two Greens senators who resigned from Parliament and his Cabinet colleague Matt Canavan, who stepped down from the frontbench, the Member for New England is refusing to go until the High Court rules on the matter.

Labor says it calls into question the very legitimacy of the Government, which holds power by the narrowest of margins.

Political correspondent David Lipson produced this story.

(Music: 'Slice of Heaven' by Dave Dobbyn and Herbs)

SCOTT LUDLAM, GREENS SENATOR FOR WA 2008-2017 (13 Jul.): So I am resigning as a senator for Western Australia and co-deputy leader of the Australian Greens, effective today.

MALCOLM TURNBULL, PRIME MINISTER ('Today', Channel Nine, 19 Jul.): And it shows incredible sloppiness on their part.

DAVE DOBBYN (sings): Hey, I got a lot of faith in ya / I'll stick with you, kid, that's the bottom line...

LARISSA WATERS, GREENS SENATOR FOR QUEENSLAND 2011-2017 (17 Jul.): It is with great sadness that I have discovered that I am a dual citizen and that I will be forced to stand down from my position in the Senate.

MALCOLM TURNBULL ('Today', Channel Nine, 19 Jul.): You have got to tick the box and confirm that you're not a citizen of another country. So it is... it's extraordinary negligence on their part.

MATT CANAVAN, NATIONALS SENATOR FOR QUEENSLAND, MINISTER FOR RESOURCES AND NORTHERN AUSTRALIA 2016-2017 (25 Jul.): I will stand aside until the matter is finally resolved and resign as the Minister for Resources and Northern Australia.

(Excerpt from 'Today', Channel Nine, 29 July)

DEBORAH KNIGHT, PRESENTER: Have you gone back: triple-, quadruple-checked your own background there?

BARNABY JOYCE, DEPUTY PRIME MINISTER: Yes.

DEBORAH KNIGHT: You're clear?

BARNABY JOYCE: I am an Australian. No problems there.

DAVE DOBBYN (sings): Hey, I got a lot of faith in ya / I'll stick with you, kid, that's the bottom line...

(Footage of Sky News, August)

PATRICIA KARVELAS, PRESENTER: Are you a New Zealand duel citizen? Your father is a New Zealander and...

BARNABY JOYCE: I am not a New Zealander. You have to apply. You can't get it by descent. You have to apply to become a New Zealand citizen. I have never applied to become a New Zealand citizen, nor do I want to. I am very proud of being an Australian citizen.

(Footage of Barnaby Joyce addressing the House of Representatives)

BARNABY JOYCE: Last Thursday afternoon the New Zealand High Commission contacted me. They considered that I may be a citizen by descent of New Zealand.

DAVE DOBBYN (sings): And living with you is a ball of a time.

BILL ENGLISH, NEW ZEALAND PRIME MINISTER: It is simply a matter of Department of Internal Affairs applying New Zealand law. They say that, unwittingly or not, he is a New Zealand citizen.

DAVE DOBBYN (sings): Howdy, angel, ooh / Where did you hide your wings?

(Footage of Barnaby Joyce addressing the House of Representatives)

BARNABY JOYCE: Needless to say I was shocked to receive this information.

JOEL FITZGIBBON, OPPOSITION AGRICULTURE SPOKESMAN: I have often said that the Deputy Prime Minister is all hat, no cowboy. And now we are entitled to even question his right to wear the hat.

BARNABY JOYCE: Given the strength of the legal advice the Government has received, the Prime Minister has asked that I remain Deputy Prime Minister and continue my ministerial duties.

TONY BURKE, MANAGER OF OPPOSITION BUSINESS: A majority of one has made a difference to who is in government and who is in opposition.

BILL SHORTEN, OPPOSITION LEADER: How can the Prime Minister possibly defend keeping him in the Cabinet and letting him vote in this House?

MALCOLM TURNBULL: The Government is very confident that the court will not find the Member for New England is disqualified from being a member of this House: very confident indeed.

TONY BURKE: This is a government without legitimacy.

MALCOLM TURNBULL: And the Deputy Prime Minister is qualified to sit in this House and the High Court will so hold!

TONY BURKE: Today was the day that the Parliament resolved it didn't know whether or not this Government had a majority and the Prime Minister was determined to cling to power, whether it was legal or not.

EMMA ALBERICI: And the Attorney-General, George Brandis, joined me earlier from Canberra.

George Brandis, thanks very much for taking the time to speak to us.

GEORGE BRANDIS, FEDERAL ATTORNEY-GENERAL: Hello, Emma.

EMMA ALBERICI: How is it tenable for the Deputy Prime Minister to continue to serve in the Australian Parliament, when a foreign country has confirmed he is one of their citizens?

GEORGE BRANDIS: Well, the reason it's tenable is because that is not the issue. I mean, I am aware of what the New Zealand Government has said today, but the legal issue here is not whether he's a citizen of New Zealand but whether, in the circumstances of this case when he had no idea at all that he was a citizen of New Zealand, according to their view, at least, of events, the disqualification in Section 4 applies to him.

Now, the Government has taken advice from the Solicitor-General, Dr Donahue. And on the basis of that advice, we are confident that, on the proper interpretation of Section 44, Mr Joyce because of his unawareness of his status as a New Zealand citizen - if, indeed, that turns out to be the case - would not be disqualified.

EMMA ALBERICI: Section 44 of the constitution is black and white on this matter: "An MP is disqualified if he or she is a subject or a citizen entitled to the rights of privileges of a subject or citizen of a foreign power." Ignorance is not considered a valid excuse. Where is the grey area you are looking to have adjudicated?

GEORGE BRANDIS: Well, I will tell you where the grey area is because there is a line of judicial authority and in particular, in two cases: Nile and Wood and Sykes and Cleary, in which a number of members of the High Court have made it very clear that section 44 can't be read in broad terms because, if it were to be read in broad terms, then it could operate in a completely irrational way.

For example, let me give you an example that was, in fact, suggested by Sir William Deane in one of those cases. Let us say a country hostile to Australia were to pass a law to say that every Australian citizen was deemed by the law of that hostile country to be a citizen of that country.

Now, if section 44 were be interpreted literally, that would mean that every single Australian citizen would be disqualified from being a member of the Australian Parliament...

EMMA ALBERICI: But, Senator...

GEORGE BRANDIS: ...which is plainly absurd. And that is the example Sir William Deane gave. So in the cases in which I have referred several of the High Court judges have said that section 44 must be given a narrower or more confined interpretation than its literal words.

EMMA ALBERICI: But what I am suggesting here is that no-one in the Australian Parliament who has been deemed to have been a citizen of another country has been allowed to continue to serve. Is that correct?

GEORGE BRANDIS: Well, let us, let us see...

EMMA ALBERICI: Is that correct?

GEORGE BRANDIS: Well, I am not in a position to tell you, actually, whether that is correct or not because there may be very old cases.

EMMA ALBERICI: But in those cases that you have cited, the parliamentarians were not allowed to continue to serve, having been deemed citizens of another country?

GEORGE BRANDIS: On the basis of the particular facts of those two cases, that is right. But the point...

EMMA ALBERICI: OK. Can we just move on? We don't want to get...

GEORGE BRANDIS: But Emma, Emma, you asked me...

EMMA ALBERICI: ...bogged down in particular details of other cases because it is complicated enough as it is.

I am curious to know what rights under law does the Prime Minister, Malcolm Turnbull, have to rule Barnaby Joyce constitutionally qualified to keep his position in the Parliament, when that decision is entirely the purview of the seven justices of the High Court?

GEORGE BRANDIS: Well, that is not quite right, either. And if I might finish my earlier answer...

EMMA ALBERICI: Well, no. Sorry. Senator, today in the Parliament the Prime Minister said: "The leader of the National Party, the Deputy Prime Minister is qualified to sit in this House and the High Court will so hold."

GEORGE BRANDIS: Well, that was the Prime Minister's view and that was his expectation.

EMMA ALBERICI: But is he entitled to...

GEORGE BRANDIS: A view? Of course he is entitled to a view.

EMMA ALBERICI: ...give what does seem to amount to a directive to the High Court...

GEORGE BRANDIS: It is not a directive at all.

EMMA ALBERICI: ...when there is a clear separation of powers?

GEORGE BRANDIS: It is not a directive at all. And the Prime Minister, who himself, by the way, is a very accomplished lawyer who has practised before the High Court, knows that better than anyone.

Of course it is not a directive. What the Prime Minister was saying was expressing a view about the law, which he expects the High Court will uphold. And that view of the law was based on Solicitor-General's advice.

And you asked me earlier on, Emma, what is the grey area? I have told you what the grey area is, because the High Court has already told us that section 44 cannot be given a black-and-white, literal interpretation and, therefore, what we must do - and this is precisely where the grey area lies - is work out what the limitations are.

EMMA ALBERICI: Why is there one rule for Barnaby Joyce and another for all other members of this Parliament who have had questions surrounding their citizenship? Matt Canavan, one of your own Senators, the former minister for resources and northern Australia, forced to step down from his role but still in the Parliament, of course. And Greens senators swiftly out, having had their own legal advice that being citizens of another country disqualified them?

GEORGE BRANDIS: Well, look, the decision that Scott Ludlam and Larissa Waters took on the basis of their legal advice, which I haven't seen, of course, is a matter for them.

But Senator Canavan and Mr Joyce are being treated in exactly the same way because they have both - the cases have both been referred to the High Court so it can adjudicate on section 44.

But hold on. Barnaby Joyce hasn't resigned his position in the Cabinet; hasn't resigned his position at all. Matt Canavan did, with you standing right beside him.

GEORGE BRANDIS: That's correct.

EMMA ALBERICI: Why has Barnaby Joyce been treated so differently?

GEORGE BRANDIS: The Prime Minister took the view that, on the basis of the Solicitor-General's advice he had received, there was no sufficient reason for Mr Joyce to resign.

Now, in the case of Senator Canavan: Senator Canavan made a decision that he would prefer to stand aside. The facts, both the facts and the legal issues in Senator Canavan's case were entirely different from the facts and the legal issues in Mr Joyce's case.

EMMA ALBERICI: If you are successful in your High Court bid to keep Matt Canavan and Barnaby Joyce in the Parliament, will you be urging the Greens to consider reinstating Larissa Waters and Scott Ludlam?

GEORGE BRANDIS: Well, that is not a matter for me. What the Greens choose to do is entirely a matter for them.

EMMA ALBERICI: Do you think they were too hasty to step down?

GEORGE BRANDIS: Well, I am not be a commentator on what the Greens choose to do, but there is a procedure - perhaps they were unaware of it - whereby these matters may be referred to the High Court under the relevant section of the Commonwealth Electoral Act. That could have been availed of by them. It wasn't.

EMMA ALBERICI: Now, just moving on to the issue of same-sex marriage: is it true, as the papers have said over the weekend, that you have been issued a directive from the Prime Minister to "run dead, avoid campaigning" on the matter?

GEORGE BRANDIS: That is not correct. No such directive has been issued.

EMMA ALBERICI: And will you be campaigning during the postal survey?

GEORGE BRANDIS: Well, Emma, I am a long-standing supporter of marriage equality, so my views are already on the public record. I am well - so it is well known that I support the 'yes' case and I will be encouraging people to vote 'yes'.

But even more importantly, I will encouraging as many people as possible to participate. Whether you believe in reforming the definition of marriage to allow gay couples to marry, or whether you believe in the status quo, the Government considers that it is very important for all Australians to have their say, which is why, having been blocked by the Senate in doing this by way of a personal attendance plebiscite, we have adopted this other course.

EMMA ALBERICI: Are you sympathetic to the views of the Catholic Church around this issue, specifically as it pertains to religious freedoms and being able to have their priests deny weddings to same-sex couples?

GEORGE BRANDIS: Well, can I make two points about that? First of all, there is only one question in the postal plebiscite and that is: "Do you think the law should be changed to allow same-sex couples to marry?" That is the only question.

It is not a question about religious freedom. It's not a question about freedom of speech. It is not a question about political correctness. It is about one issue and one issue only: that is whether the law should be changed to allow same-sex couples to marry.

However, in Senator Smith's bill, which is the private member's bill currently under discussion, just as in the exposure draft that I prepared that was released at the time of the plebiscite debate last year, there were extensive protections of religious freedom.

And one of the points that people like Archbishop Fisher need to remember is that, if the Labor Party were in charge of this process, there wouldn't be the protections of religious freedom that a Coalition private member's or senator's bill will guarantee.

EMMA ALBERICI: Senator Brandis, thanks for your time.

GEORGE BRANDIS: Thank you, Emma.