The Turnbull government is putting on a brave face as its numbers in the House of Representatives dwindle, saying it still has the support of an independent if Labor forces a motion of no confidence.
However, there are still two weeks before the lower chamber sits again and there is no guarantee what its make-up will look like by then.
Leader of the House Christopher Pyne declined to give a guarantee that any more government MPs won't become embroiled in the citizenship debacle.
"Nobody can," he told Sky News on Sunday.
A cloud hangs over Liberal chief whip Nola Marino whether she is an Italian dual citizen through marriage.
Prime Minister Malcolm Turnbull said that situation had been dealt with by the High Court case in which Senator Matt Canavan was cleared of holding dual Australian/Italian citizenship.
But senior Labor senator Penny Wong said Mr Turnbull is wrong and the High Court considered Italian citizenship by descent, not citizenship by marriage, while a number of experts have stated that citizenship by marriage is automatic.
"He is covering up for Nola Marino just like he and his ministers covered up for Stephen Parry (the former Senate President)," Senator Wong told AAP.
"If this is really his only defence, then this case needs to be referred to the High Court."
Mr Pyne has threatened to hold a vote when the house returns on November 27 to refer Labor MPs Justine Keay and Susan Lamb to the High Court, because he believes there are doubts over their citizenship status at the time of the 2016 election.
Labor argues both took sufficient steps to renounce their foreign citizenship, unlike Barnaby Joyce, Stephen Parry, Fiona Nash and John Alexander.
Mr Alexander resigned on Saturday to fight a by-election after he admitted he most likely held UK citizenship at the time of the election.
Independent MP Bob Katter says the cross bench will move immediately on a royal commission into the banks following the Mr Alexander's resignation.
Mr Katter on Sunday said the crossbenchers now hold the balance of power and would move immediately on the royal commission and on the issue of ethanol when the House returns.
House of Reps Speaker Tony Smith has yet to announce when Mr Alexander's Bennelong by-election will be held, but it is expected before the end of the year.