A measure to force jobseekers under the age of 25 to wait an additional four weeks before accessing unemployment benefits has been shot down in the Senate.

The social services legislation amendment (youth employment and other measures) bill was defeated on its second reading, 30 votes to 35.

Labor and the Greens were against the measure, which was announced in the May federal budget, meaning that the government needed the support of six of the eight crossbenchers to pass the bill.

Only two crossbenchers – Family First’s Bob Day, and Liberal Democrat David Leyonhjelm – voted with the government.

The independent senator John Madigan abstained, and the remaining five senators – independents Jacqui Lambie, Glenn Lazarus and Nick Xenophon, Palmer United senator Dio Wang and Motoring Enthusiasts party’s Ricky Muir – voted against the bill.

Wang told Guardian Australia the measures in effect punished young people who could not find work. “It’s reasonable to try to push teenagers and young people to get a job,” he said. “The problem is, there’s not enough jobs around.”

Xenophon said he had “deep concerns about the practical impact of these changes at a time when unemployment was rising and some were even predicting Australia was heading for a contraction in our economy”.

But on Wednesday morning, before the bill was shot down, the social services minister, Scott Morrison, vowed to push ahead.

“We remain absolutely committed to the measures we’ve brought to the parliament on this issue,” Morrison said. “We do not believe that we should be sending a message to young people that it should be OK to go from the school gate to the Centrelink front door, and that’s why we’re bringing these measures.

“Labor and others may choose to oppose that, and that is their democratic right. The Coalition remains absolutely committed to this policy.”

Labor criticised the bill, saying it would force young people into poverty. The opposition families spokeswoman, Jenny Macklin, said the government’s agenda was in “disarray”.

“Scott Morrison was supposed to mop up the mess left by the bumbling Kevin Andrews, but Scott Morrison has been forced to repeatedly withdraw bills before being debated,” Macklin said. “If he spent a bit less time trying to get his head on television every day, he might be doing a better job.”

The bill would freeze dole payments for those aged under 25 for four weeks on top of the existing one-week waiting period, and also would have extended the age of eligibility for the Newstart allowance from 22 to 24, at a cost to jobseekers of about $48 a week.

The four-week waiting period was introduced in May, after a public backlash forced the government to back down on a 2014 budget savings measure that would have seen the dole frozen for those under 30 for six months. That would have saved the government $1.2bn.

The Greens senator Rachel Siewert said: “The federal government could not get their attempts to make young people wait six months for income support through, and they have now failed at pushing through a watered-down measure of one month.

“Instead of trying to polish up fundamentally bad policy, they should realise that dropping young people off income support is yet another barrier to employment.”