For the first time since federation, a federal government has voted for an inconsequential second reading amendment accusing itself of failures.
The procedural error forced parliamentarians back into the chamber to vote again for a bipartisan bill they believed had passed.
Labor's Andrew Leigh in parliament on Wednesday moved the amendment to international tax legislation, calling on the government to "explain why it has failed to close tax loopholes and increase transparency in Australia".
Usually, that would be voted down before the bill passed the House of Representatives but Assistant Treasurer Kelly O'Dwyer seemingly forgot and moved the bill through its final stage.
The Speaker's chair did not advise her otherwise.
Second reading amendments are used to make statements rather than to alter legislation.
But due to a procedural issue it meant the bill didn't pass and the amendment was agreed to instead.
Speaker Tony Smith recalled members to deal with the mistake.
Manager of opposition business Tony Burke said the error showed the coalition was incompetent.
"There has never been a more chaotic government, there has never been a more chaotic parliament," he told the chamber on Wednesday.
But leader of the house Christopher Pyne described it as an inadvertent human error caused by a series of events.
"It's something I would have done when I was manager of opposition business," he said.
"We're really arguing the toss over something that's not very important, we all support the bill."
It comes after the coalition - which holds the slimmest possible majority in the lower house - was caught out on a series of votes when several MPs left work early on the first Thursday of parliament after the July election.
