Malcolm Turnbull has rolled the dice on the workplace law triggers for the double-dissolution election, which cut his government's majority to a single seat.
The opposition scuttled the prime minister's plan to kick off the first full working day of parliament by delivering on his election promises, with Labor moving to set up a banking royal commission along with another motion condemning the government over a lack of economic leadership.
The tight numbers - 76 government MPs to Labor's 69 with five crossbenchers - were highlighted when a vote on the banking inquiry motion went in the government's favour 75-73.
Labor cried foul because the government had not granted a "pair" to MP Clare O'Neil, who was unanimously allowed parental leave from parliament on Tuesday.
Leader of the House Christopher Pyne said Labor had not specifically sought a pair, but the Liberal frontbencher himself had promised in writing two weeks ago MPs would "always" get a pair in case of illness or family emergencies.
After another Labor attack, over a report the prime minister had been rolled by his cabinet on changes to negative gearing, Mr Turnbull finally introduced a bill to protect emergency services volunteers, which he had promised during the election amid a dispute over Victoria's CFA and the firefighters union.
He also brought back to parliament bills to reinstate the Australian Building and Construction Commission and put in place tougher governance rules on unions and their officials.
If the bills fail again, parliament could hold a rare joint sitting of both houses to pass them.
Treasurer Scott Morrison introduced a bill to make more than $6 billion in budget savings, which he expected Labor to support, as it included measures the opposition took to the election.
Opposition backing is also expected for a hike in tobacco taxes.
In the first question time, the prime minister and Treasurer Scott Morrison fended off Labor attacks over Medicare, the banking royal commission, superannuation policy and a coalition backbench revolt aimed at watering down race hate laws.
"When will the prime minister start leading his party and not following his party?" Labor leader Bill Shorten asked.
Mr Turnbull reminded the opposition leader of his post-election promise to be "constructive".
"What we've had from the moment the house opened this morning (is) ... one political stunt after another."
The Senate got off to a rocky start with Labor frontbencher Sam Dastyari explaining why he allowed a Chinese donor to foot the bill after he exceeded his travel allowance.
The senator told parliament he should have paid the $1670.82 bill - which was properly disclosed under parliamentary rules - and had now donated that amount to charity.
But Liberal senator Cory Bernardi said the explanation was "wholly inadequate", while coalition colleague Eric Abetz said it was a test of Bill Shorten's leadership whether Senator Dastyari should remain in the shadow ministry.
A deal was approved ensuring the first six senators elected in each state at the election eight weeks ago will get six-year terms while the remainder will be up for re-election in three.
