Federal politicians who "honestly swear" they were unaware of being dual citizens should not be disqualified from parliament, the attorney-general has told the High Court.
The High Court will next week examine the eligibility of seven politicians, including Deputy Prime Minister Barnaby Joyce and two government senators, caught in a constitutional tangle over dual citizenship.
Australians with dual citizenships are banned from entering federal parliament under section 44 of the constitution, which wards against split allegiances.
Attorney-General George Brandis has argued the oath of parliamentarians should be accepted if they were unaware there was a "considerable, serious or sizeable prospect" of being a foreign citizen.
"If there is material that contradicts such a claim, then the matter can be tested, as occurred in relation to Senator (Malcolm) Roberts," the attorney argued in submissions lodged with the High Court on Friday.
"Otherwise, the oath of the parliamentarian should be accepted, and no question of disqualification would arise, provided reasonable steps were taken to renounce foreign citizenship within a reasonable time of the parliamentarian becoming aware of his or her status."
The government has argued Mr Joyce and Nationals senators Fiona Nash and Matt Canavan have not fallen foul of the constitution because they did not know they were foreign citizens.
It has made the same argument for independent Nick Xenophon and former Greens senator Larissa Waters, who acquired citizenship either by descent or change in foreign law.
However, it has argued One Nation's senator Roberts and former Greens senator Scott Ludlam should be ineligible, because they were born overseas and failed to sever their citizenship by birth.
Former independent MP Tony Windsor, who has joined the case against Mr Joyce, this week argued allowing him to remain in parliament would reward carelessness.
Mr Windsor's lawyers argued that letting the Nationals leader off the hook would encourage future candidates not to properly investigate whether they were dual citizens, because they'd face no consequence for being ignorant.
Senator Brandis rejected these claims, along with the argument that simply being a dual citizen was enough to disqualify a parliamentarian.
"Without any knowledge of present or past citizenship there can be no risk of split allegiance," the attorney argued.
"In the context of that actual knowledge, the choice not to take all reasonable steps to renounce that citizenship marks its retention as voluntary."
The High Court has set down three days for hearings from Tuesday.
