The Turnbull government has suffered an embarrassing blow to its narrow majority after it lost three consecutive votes in the lower house.
It's believed to be the first time in five decades that a majority government has lost a vote in the House of Representatives.
Labor exploited a weakness in the government's numbers late Thursday afternoon when many MPs were leaving Canberra for home.
The opposition tried to bring on debate in a bid to call on Prime Minister Malcolm Turnbull to establish a royal commission into banks.
Labor then won three divisions in its attempt to expedite debate, taking advantage of the coalition's slender majority.
Speaker Tony Smith was also forced to use his casting vote - believed to be for the first time - on a procedural motion to allow the debate to be considered.
Treasurer Scott Morrison denounced the move and accused Labor leader Bill Shorten of taking political advantage.
"He is using a stunt to promote his stunt," he told parliament.
Mr Shorten said the royal commission was the last resort for justice for those who'd been let down by the banking system.
"We may succeed tonight or not .... we will never give up."
Shadow treasurer Chris Bowen urged the prime minister to give up the fight against a royal commission.
"Sometimes you just have to know when you've lost - sometimes you just have to know when it's time to recognise reality ... when it's time to say 'OK I might have got this one wrong'."
Other Labor MPs were celebrating the victory on social media.
"How is that stable majority government working out for you, Mr Turnbull?" frontbencher Mark Dreyfus tweeted.
Former prime minister Tony Abbott says the Turnbull government has lessons to learn after it suffered an embarrassing vote loss in the lower house.
The opposition, in celebration mode over the victory, said it took just two sitting days for the government's majority to collapse.
The coalition was on notice.
"Tonight's been a wake-up call for the Turnbull government - the clock is ticking," manager of opposition business Tony Burke said.
Government whip George Christensen suggested coalition MPs were not heeding calls to be in the chamber.
"They wouldn't turn up for the vote," he said.
"That's baptism by fire."
Manager of Government Business Christopher Pyne told the Nine Network on Friday he didn't give MPs permission to leave early, but there wasn't any point in pointing fingers.
"There is no doubt what happened late yesterday afternoon was a stuff-up and those people who weren't there obviously they learnt a valuable lesson, in fact everyone learnt a valuable lesson," he said.
"It's a salutary lesson for anyone who went home before the house rose yesterday afternoon."
The cabinet minister refused to be drawn on what Mr Turnbull will say to his colleague Michael Keenan who was on a flight at the time of the votes.
"People out there in the community are more worried about jobs, more worried about feeding themselves and their children than they are about three adjournment votes in the House of Representatives," he said.
Mr Abbott said it was important to note that the government was back in control after a brief period.
But the outcome would be studied.
"There's a sense in which all of us are learning lessons all the time - whether you're a journalist, a member of parliament, a whip or even a prime minister.
"I'm sure there will be lessons that everyone will learn out of this week."
Labor indicated it would continue testing the government's majority, saying the victory built the case for a future no-confidence motion.
"It doesn't stop tonight," Mr Burke said.
Labor frontbencher Anthony Albanese described the events as a farce.
"If you can't run the parliament, you can't run the country," he said.
"We were in control during three years of minority government, each and every day of the parliament. This mob with a majority government couldn't get through three days."
During debate, Treasurer Scott Morrison denounced the move and accused Labor leader Bill Shorten of taking political advantage.
"He is using a stunt to promote his stunt," he told parliament.
Mr Shorten said the royal commission was the last resort for justice for those who'd been let down by the banking system.
"We may succeed tonight or not .... we will never give up."
