The government "won't hesitate" to refer a Labor MP to the High Court over citizenship doubts, says Leader of the House Christopher Pyne.
But Mr Pyne says no timeframe has been put on the referral of Queensland MP Susan Lamb and the government would prefer Labor leader Bill Shorten to make the decision.
Ms Lamb is a British citizen by descent, but argues she took all reasonable steps to renounce it in time to run for the July 2016 federal election.
Authorities told her in a letter in August 2016 the UK Home Office could not process her renunciation because it could not be satisfied from the documents available that she held British citizenship.
Mr Pyne said Ms Lamb's case was "clearly deficient" and she should be referred to the High Court to test her eligibility for parliament under section 44 of the constitution, which bans dual nationals.
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"Our preference is that Labor do the right thing and refers it own members, but we won't hesitate to use our numbers to make sure that everyone sitting in the parliament is legitimately elected," Mr Pyne told Sky News on Thursday.
Asked if the government would make the referral when parliament resumes on February 5, Mr Pyne said: "We are not putting a timeline on these matters."
