Anyone who dares predict what will happen in federal parliament this week is being very brave, senior Labor MP Tony Burke says, as the opposition prepares to test the government's shaky numbers.
Malcolm Turnbull's removal as prime minister has robbed the government of its one-seat majority.
If all lower house crossbenchers vote the same way as Labor, the votes would be even, and the Speaker would be forced into a casting vote.
Labor is expected to play on the chaos by seeking to refer Peter Dutton to the High Court, with the Greens to move a no confidence motion in the home affairs minister.
"I think anyone who wants to predict how this week is going to go is being very brave," Mr Burke told ABC radio on Monday.
Scott Morrison has already copped bad news ahead of his first Question Time as prime minister.
The latest Newspoll shows the coalition has slipped further backwards in two-party preferred terms, lagging Labor 44 to 56 per cent.
The result will energise the Labor opposition, who will seek to pummel the government in question time over why they felt Mr Turnbull had to go.
"We have a government here now ... that is divided, that is illegitimate, that doesn't know why it's there, and you bet we'll pursue that," Mr Burke said.
Finance Minister Mathias Cormann said the government was focused on the issues that matter to voters.
"The Labor Party always pulls stunts," Senator Cormann told reporters at Parliament House.
Mr Dutton, who failed to become prime minister on August 24, is expected to come under pressure on two fronts - the au pair visa affair and his eligibility to sit in parliament.
Mr Burke argued Mr Dutton should refer himself to the High Court after he "misled the parliament" and supports a motion of non-confidence in him.
"There is no doubt a legal question mark. He has a very important job for Australia and it is essential it is done lawfully. The right thing to do is self-referral," he said.
Nationals deputy leader Bridget McKenzie said it was a decision for Mr Dutton whether he referred himself.
Ms McKenzie said when parliament and MPs don't tackle the real issues, punters punish them at the polls, as seen in the NSW by-election in Wagga Wagga.
Several MPs, including Mr Morrison's deputy and Treasurer Josh Frydenberg, won't be in parliament as they take time out to commemorate Rosh Hashanah, the Jewish new year.
Australian Associated Press