Senior minister Christopher Pyne expects three Labor MPs to resign if the High Court rules against Katy Gallagher in her citizenship case.
A decision on the ACT Labor senator's eligibility to sit in the Senate is expected soon.
Mr Pyne said Labor MPs Josh Wilson, Justine Keay and Susan Lamb were in similar situations.
"If Katy Gallagher is ruled out by the High Court, you would assume those three would resign from the parliament and there would be by-elections in those seats," Mr Pyne told Sky News on Tuesday.
Mr Pyne said if Labor didn't force the MPs to resign the government would examine whether they should be referred.
"I don't think we'll get to that point ... I'm sure they will themselves come to the sensible conclusion," he said.
The Gallagher case was heard on March 14, but the court reserved its decision.