Moderate Labour MPs are planning a “reasoned amendment” to oppose the government’s disability benefit cuts, Sky News understands.

Nearly 100 Labour MPs are understood to have given their backing to this measure, which means the government could be defeated on its flagship welfare reforms.

MPs who have not yet gone public with their criticisms have signed the motion, calling for a delay to assess the impact of cuts to personal independence payments (PIP).

They express concerns, according to a draft seen by Sky News, about the government’s own figures showing 250,000 people could be pushed into poverty, and what the forecast is for how many may find employment.

The reasoned amendment was tabled by Dame Meg Hillier, chair of the Treasury select committee, with the support of 12 other select committee chairs.

Other senior figures, who are normally loyal to the party leadership, are understood to be spearheading the reasoned amendment, which would need to be selected by Commons Speaker Sir Lindsay Hoyle when MPs debate the legislation next week.

It is an attempt to force the government to water down the benefit changes, in advance of the vote. It is understood that 99 MPs had signed it by Monday evening.

The amendment emerged as Work and Pensions Secretary Liz Kendall was addressing the weekly gathering of Labour MPs and peers to sell the reforms to PIP and universal credit. The government argues the welfare bill is rising “unsustainably”.

Opponents of the changes to sickness and disability benefits say opinion among Labour MPs has hardened since the draft legislation was published last week.

Dozens of MPs are said to have expressed concerns to party bosses, including junior ministers and aides. A party whip resigned her post last week to oppose the reforms.

Some MPs, who have not yet spoken publicly, told Sky News the chances of the government losing the vote were “under-priced”.

It is understood that No 10 officials have told concerned MPs they would be “voting with Nigel Farage” and “will bring us all down” if they vote against the changes.

On Monday night, Ms Kendall told a meeting of Labour MPs that they must back the changes, saying the survival of the welfare state depended on it.

Some current PIP claimants are set to lose their benefits when they are reassessed from the end of next year.

Ms Kendall said: “There is no route to social justice based on greater benefit spending alone.

“The path to fairer society – one where everyone thrives, where people who can work get the support they need, and where we protect those who cannot – that is the path we seek to build with our reforms.

“Our plans are rooted in fairness – for those who need support and for taxpayers.

“They are about ensuring the welfare state survives, so there is always a safety net for those who need it.”

The first vote on the legislation is next week, and a defeat would be a major blow to Sir Keir Starmer’s plans to cut the welfare bill, which the government say is becoming “unsustainable”.

Ms Kendall has been reassuring MPs that nine out of 10 PIP claimants will keep their benefits, and those who are most vulnerable will be protected.