Federal Labor is confident backbencher Susan Lamb is eligible to be sitting in parliament despite the government calling for her resignation over dual-citizenship concerns.
Labor frontbencher Chris Bowen said the party was "very confident" Ms Lamb would survive a High Court referral over her British citizenship.
Mr Bowen insisted if Ms Lamb was referred to the High Court over dual-citizenship concerns, then government MPs should be sent with her.
"If there are going to be referrals to the High Court, it should be done on that basis that everyone that has got questions to answer should be referred to the High Court," Mr Bowen told reporters in Sydney on Monday.
The Turnbull government is seeking the resignation of Ms Lamb and has threatened to use its renewed majority in the lower house to refer her to the High Court.
However, Mr Bowen said if the government used its numbers in the House of Representatives to change how MPs were referred "it would say more about them than it does about Susan Lamb".
"This government just continues to play cheap political point scoring," Mr Bowen said, accusing it of running a "protection racket" for its own MPs.
"She clearly took reasonable steps, unlike Barnaby Joyce and Fiona Nash and the rest who did nothing. She contacted the Home Office, sought to renounce her citizenship."
The British Home Office did not accept Ms Lamb's application to renounce her citizenship and she failed to supply them with a copy of her parents' marriage certificate, The Australian reports.
But Mr Bowen said there were "some personal circumstances" that made it difficult for Ms Lamb to access that document.
Mr Bowen says Labor is happy to have Ms Lamb's case tested in the High Court so long as other government MPs such as Julia Banks join her.
"We weren't saying it should be only Liberal MPs and National party MPs referred, we said 'Refer those for whom there are questions to answer'," Mr Bowen said.
"The government did not want that to happen - what are they hiding?"
Tasmanian Liberal Senator Eric Abetz says acting Opposition Leader Tanya Plibersek should use her visit to Hobart on Monday to announce Labor MP Justine Keay is resigning over her citizenship.
"In Tasmania, (former Senate president) Stephen Parry and (crossbencher) Jacqui Lambie did the honourable and decent thing and resigned when it was clear that there was an issue," he said.