Of the seven federal MPs hauled before the High Court over their citizenship status, only One Nation's Malcolm Roberts and Greens senator Scott Ludlam were wrongfully elected, the Commonwealth contends.
In its official submission to the High Court the government says the other five politicians - Nationals Barnaby Joyce, Fiona Nash and Matt Canavan; Queensland Green Larissa Waters; and crossbencher Nick Xenophon - should be cleared because they were ignorant of their status.
If the court agrees, it could pave the way for Ms Waters to return to Parliament immediately.
All seven politicians were referred to the High Court after discovering they held dual citizenship - which is forbidden under Section 44 of the constitution - over the last three months.
The Commonwealth's submissions argue the court should find that only those who have "voluntarily obtained or retained" foreign citizenship should be disqualified. Anyone who "does not know that they are, or ever were, a foreign citizen" should not be ruled ineligible, the submission filed on Attorney-General George Brandis' behalf says.
"A person who becomes aware that he or she is a foreign citizen, or who becomes aware [ie subjectively appreciates] that there is a considerable, serious or sizeable prospect that he or she has that status, voluntarily retains that status unless he or she takes all reasonable steps to renounce it within a reasonable time of becoming so aware.
"Alternatively, where a person has no knowledge that they are, or ever were, a foreign citizen, the requirement to take 'all reasonable steps' to renounce that foreign citizenship does not require the person to take any steps. Taking no steps is reasonable in these circumstances," the submission said.
My Joyce - the deputy prime minister and Nationals leader - and Senators Nash, Canavan and Xenophon all argue they had no knowledge of their "citizenship by descent" status.
While Senator Waters has already quit Parliament over her Canadian heritage, she would be free to reclaim her seat if the court agreed with the Commonwealth's argument. The Greens would merely need to nominate her to replace the vacancy she left behind.
The court has already ruled that Senator Roberts was a British citizen when he nominated last June, and he did not successfully renounce until December - five months into his tenure. It is widely believed he will be disqualified at further High Court hearings next month.
Mr Ludlam was the first to resign over the citizenship issues after discovering he was a New Zealand citizen.
The government is hoping Mr Joyce in particular fends off the challenge to his eligibility because that would force a byelection in his seat of New England and put Prime Minister Malcolm Turnbull's slender majority at risk.
The court will hold hearings into the matter between October 10 and 12.
