Labour's frontbench team put "significant pressure" on MPs to abstain during a crucial vote on emergency retrospective welfare legislation, a recently resigned parliamentary private secretary has told the Guardian.

Ian Mearns MP said he voted against the government's jobseekers (back-to-work schemes) bill on Tuesday because he thought the unemployed were already suffering enough from "Kafkaesque" benefit sanction decisions made by the Department for Work and Pensions (DWP).

The fast-tracked bill, which seeks to overturn the outcome of a court appeal ruling on the Poundland case, is expected to be passed into law early this week.

It will ensure that the DWP no longer has to pay £130m in benefit sanction rebates to 250,000 jobseekers by retrospectively making lawful regulations deemed unlawful by three senior judges since February.

Mearns said that after passing through the Commons' no lobby he sent a text to his former boss, the shadow secretary for international development, Ivan Lewis, and the party's chief whip, Rosie Winterton, saying he had resigned.

"I was under no illusions that I would be sacked if I voted against the party wishes. So immediately on having gone through the no lobby and having voted against the government bill, I then texted both the chief whip and the shadow secretary of state for international development … to say, with a heavy heart, I resign."

"Among 43 or 44 Labour MPs who voted [against the bill], I was the one who had the PPS position. But I know a significant amount of pressure was brought to bear on other colleagues in similar positions.

"There were an awful lot of people who were clearly unhappy … well over half of the parliamentary Labour party were clearly uncomfortable with the position that was taken by the leadership," Mearns said.

The Gateshead MP said that during last Monday's weekly meeting of the parliamentary Labour party "there wasn't a single person in the room who spoke in agreement with the position being put forward by the leadership team".

His description of the meeting was confirmed by other MPs who did not want to be named.

Mearns said the rebellion by over 40 Labour MPs included a former chief whip, Nick Brown, former housing minister John Healey and a former junior minister, Derek Twigg.

"These people aren't the usual suspects. I think the frontbench had their reasons [for wanting everyone to abstain from voting] but I must admit, I still don't completely understand why we were put into that position in the first instance."

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One Labour source said the shadow chancellor, Ed Balls, had not wanted to lose fiscal credibility on the eve of the budget by being seen to be favouring a £130m payout to benefit claimants.

Mearns criticised his own shadow frontbench for misunderstanding the nature of the benefit sanctions regime.

"It just seems to me that our frontbench stance is that everybody who's been guilty of some sort of [benefit] infringement and had a sanction against them since 2011 is someone swinging the lead or taking a political stance," he said.

"Gosh, I really do wish there were that many thousands of people who were willing to take a political stance and lose benefits for the sake of putting a marker down against workfare … I just don't think that's the case at all."

Mearns spoke as disgruntled Labour MPs prepared to vent more rage at Monday's planned meeting of the parliamentary Labour party. Many who obeyed the order to abstain anticipate an angry reaction from union backers and activists in their constituencies. "There is a lot of anger still because we were forced to do something that we knew was wrong," he said.

Ed Miliband is not expected to attend the meeting but a source said Liam Byrne, the shadow work and pensions secretary and target of much ire, is likely to be, adding: "The feeling is that left to his own devices we would consistently be voting with the Tories. We urgently need to develop a distinctively Labour approach on welfare and not just keep following the Tories."