The federal government could be forced back to the drawing board on tougher citizenship laws after its legislation was sunk in parliament.
The proposed changes would have extended the waiting time for permanent residents to apply for citizenship, and created tougher English language tests and extra powers for the minister.
They were struck off the Senate notice paper on Wednesday night.
While the government made a last-ditch amendment to lower the English standard from "competent" to "modest", it wasn't enough to drum up support from Nick Xenophon's bloc of three votes.
The government failed to meet a deadline to bring the legislation on for debate, meaning they could be forced to make changes before reintroducing the bill to parliament.
With Labor and the Greens opposed, the legislation was discharged by a rarely used Senate procedure.
Greens senator Nick McKim told AAP the ball was back in Immigration Minister Peter Dutton's court.
"I have no doubt this legislation was intended to take Australia back down a pathway to a White Australia policy," Senator McKim said.
Mr Dutton's office said negotiations with crossbench senators would continue, foreshadowing the government's intention to persist with the reforms.