Another federal by-election is possible with the Government demanding Labor MP Susan Lamb resign from Parliament.
"Susan Lamb and the Labor Party have been engaging in a great big cover-up since the middle of last year," Liberal Cabinet Minister Simon Birmingham said this morning.
The Government argues there is a, "black-and-white case" Ms Lamb is a British citizen, and has pointed out her British barrister Adrian Berry stated she is a British citizen.
Ms Lamb tried to renounce her British citizenship, but the UK Home Office said she had not provided enough evidence for them to ascertain her citizenship and therefore it could not be renounced.
The Government argues that means Ms Lamb is a dual citizen and is ineligible to stay in Parliament.
Manager of Government Business Christopher Pyne said Ms Lamb should resign straight away.
"She should have resigned months ago, like John Alexander did," Mr Pyne said.
He accused Labor leader Bill Shorten of weakness for failing to force her to go.
Mr Pyne argued Ms Lamb did not need to be referred to the High Court to have her case tested because he said it was already clear.
"There's nothing for the High Court to find with Susan Lamb," he said.
But Mr Pyne did not rule out the Government using its numbers in the House of Representatives to refer her case to the High Court.
"We will refer if necessary if Labor refuses to do the right thing," he said.
Other MPs not convinced referrals for the best
Coalition backbencher Scott Buchholz warned the Government should not take that step.
"I think it's a dangerous precedent to have government referring members," Mr Buchholz said.
He would not guarantee he would vote for a motion to send Ms Lamb to the High Court.
"I will cross that bridge when we get to it," Mr Buchholz said.
"I spoke with Susan as well as others in the mix. She's a good operator. She's having a crack."
Manager of Opposition Business Tony Burke said every MP with a question over their citizenship should be referred to the High Court or there would be a "ridiculous outcome" where the issue would dominate the entire year.
Mr Burke pointed out Labor moved in Parliament late last year to refer a group including Ms Lamb, crossbencher Rebekha Sharkie as well as some Liberals to the High Court but the Government voted against the motion.
He said everyone with a question over their citizenship should be referred to the High Court so their eligibility could be determined and the issue finalised.
A by-election will be held for the inner-Melbourne seat of Batman following Labor MP David Feeney's resignation last week.
The Government argues Ms Lamb should quit immediately so the by-election for the regional Queensland seat of Longman can be held at the same time.
Longman is an extremely marginal seat, Ms Lamb narrowly won it from former minister Wyatt Roy at the 2016 election.