High-profile Tasmanian senator Jacqui Lambie has become the latest casualty of the citizenship crisis engulfing federal parliament.
Senator Lambie - the daughter of a Scottish-born father - on Tuesday revealed UK authorities had confirmed her status as a British citizen by descent.
As a result, she was ineligible to contest the 2016 election and sit in parliament.
"I didn't think I actually had a problem with it, so I never gave it a second thought " she told LAFM radio in Launceston of her newly-confirmed status.
Senator Lambie will make a statement to parliament about 12.40pm (AEDT).
Her replacement in the upper house will be determined by the High Court.
Steve Martin was next on the Jacqui Lambie Network Senate ticket at the 2016 election, but there are doubts about his eligibility to sit in parliament.
Senator Lambie's announcement came as the Turnbull government ramped up pressure on Labor Leader Bill Shorten over the citizenship credentials of opposition MPs.
"Bill Shorten has been playing a very dodgy game in this business from start to finish," Attorney-General George Brandis told the Nine Network.
The onus was on the opposition leader to live by the same standard he has demanded of the government, he said.
A resolution passed in the Senate on Monday requires senators to make declarations about all relevant particulars of their citizenship in a special registry by December 1.
A similar motion is expected to be passed in the House of Representatives when it meets in a fortnight.
Prime Minister Malcolm Turnbull, speaking from Manila where he's attending the East Asia summit, said the registry plan will get all the facts on the table.
"Then the House can consider them and then, if they wish, refer people to the High Court," he said.
The government is keen to refer at least two Labor MPs - Justine Keay (Tasmania) and Susan Lamb (Queensland) - who were still British citizens when nominations for the 2016 election closed.
Labor insists they are safe because they took all reasonable measures to renounce UK citizenship.
"I don't accept that Labor MPs are not qualified to sit in the parliament," Mr Shorten told reporters in the Sydney seat of Bennelong where he announced former NSW premier Kristina Keneally will contest the December 16 by-election.
"But I do accept that the Turnbull government ... has so fundamentally mismanaged this citizenship crisis that there is now also not just a crisis of faith in the government but indeed the operation of the parliament."
