Labor will use parliament's final sitting fortnight to tighten the screws on Home Affairs Minister Peter Dutton over his eligibility to be an MP.
Opposition Leader Bill Shorten said it was "long past the day" for Mr Dutton and Victorian Liberal MP Chris Crewther to have the High Court test whether they were in breach of the constitution.
"I think the parliament needs to see what we can do about that matter rather than the government running a protection racket for people with clouds over their constitutional eligibility," Mr Shorten told reporters in Melbourne on Friday.
Mr Dutton has faced questions about whether he has a financial interest in publicly-funded Brisbane childcare centres owned by his wife.
He has repeatedly denied doubt over his eligibility, citing legal advice and dismissing the issue as politically-motivated after it re-emerged during his failed bid for the Liberal leadership.
Mr Crewther is under a cloud after investing in a pharmaceutical company which was associated with a university research grant.
Section 44 of the constitution disqualifies anyone who has a "direct or indirect pecuniary interest" in any agreement with the Commonwealth.
Mr Shorten said there were a lot of question marks surrounding the pair.
He confirmed the opposition had been in discussions with crossbench MPs, who could deliver successful referral motions if they added their six votes to Labor's 69.
However that appears unlikely after the government shored up maverick Queensland MP Bob Katter with a $234 million agreement to fund water projects in his electorate.
Labor could have an eligibility headache of its own with South Australian MP Tony Zappia on Wednesday forced to reject claims he could be ineligible over his interest in an Adelaide gym.
