One of Australia's most respected barristers says three more lower house MPs, including two Labor members, would likely be disqualified from Parliament by the High Court.
David Bennett, QC, who served 10 years as Commonwealth Solicitor-General and successfully acted for senator Matt Canavan in the recent High Court case, has provided legal advice to the Liberal Party that Labor's Justine Keay and Susan Lamb and NXT MP Rebekha Sharkie would all fall foul of section 44 (i) of the constitution, which forbids dual nationals from being elected.
"On the basis of the facts with which I have been briefed, in my view all three members were so disqualified, but this view cannot be expressed with absolute certainty," Mr Bennett wrote.
The release of the legal advice on Friday will build pressure for the two Labor MPs, Ms Sharkie, and possibly WA Labor MP Josh Wilson to be referred to the High Court by the Parliament to have their cases tested - a move Labor has so far resisted.
On Friday, Liberal Hollie Hughes, who was set to replace former deputy Nationals leader Fiona Nash in the Senate, was referred to the High Court.
Ms Hughes was recently appointed to the Administrative Appeals Tribunal, which could disqualify her under section 44 (iv) of the constitution for holding an office of profit under the crown - even though she had no conflict at the time of the July 2, 2016 poll.
The Nationals are already working on a plan to parachute Ms Nash back in to the Senate, and have received legal advice from Bret Walker, SC. A casual vacancy could be created if Ms Hughes is disqualified and Ms Nash could fill it, though Liberal candidate and former general Jim Molan is next in line and would likely fight the move.
Both Ms Keay and Ms Sharkie have confirmed they did not receive formal confirmation of renunciation of their British citizenship until after nominations for the 2016 election closed on June 9, while Ms Lamb has refused to say when renunciation took effect.
Mr Bennett stated in his advice the "three members were British citizens at the time of their nominations" and that, given each was able to renounce her British citizenship by filling out a form and paying a fee, there was nothing "irremediable" about their status as UK nationals.
In its recent judgment on the "citizenship seven", the High Court found a person could not be "irremediably" disqualified from being elected if they had taken all reasonable steps to renounce dual nationality - but this clause is thought to apply to countries that, for example, do not allow a person to renounce citizenship, as in the case of the Iranian-born Labor senator Sam Dastyari.
"There is no serious question that UK law or practice fell into that category," Mr Bennett wrote.
Labor has so far insisted that Ms Keay and Ms Lamb took all reasonable steps to renounce and were therefore in the clear, while Ms Sharkie made a similar point on Thursday when she revealed her renunciation took place after June 9, 2016.
On Friday, Opposition Leader Bill Shorten said his party was "not ruling out that anyone shouldn't go to the High Court. But what we are saying is let's get every parliamentarian to put all their facts on the payable. Let's have a common disclosure standard".
Mr Shorten and Prime Minister Malcolm Turnbull have so far failed to agree on how to end the impasse on implementing a disclosure regime.
But Mr Bennett dismissed Labor arguments that Ms Keay and Ms Lamb were in the clear, pointing out former Senator Nash renounced her British citizenship in three days, thereby dismissing the "reasonable steps" argument, but conceding that Ms Sharkie - who acted to renounce 49 days before nominations closed and succeeded after 71 days - had a stronger "reasonable steps" argument than the Labor pair.
Ms Lamb began the process of renouncing just 17 days before nominations closed, while Ms Keay acted 27 days before - despite being told by Labor officials in February 2016 she needed to act.
The High Court on Friday gave the green light to former Australian Democrats leader Andrew Bartlett taking former Greens senator Larissa Waters' place in Queensland; Fraser Anning will take the Queensland One Nation seat vacated by Malcolm Roberts and Jordon Steele-John will replace Scott Ludlam as Greens senator for Western Australia.