Sir Keir Starmer is facing the biggest Labour rebellion of his premiership to date after more than 100 of his own MPs backed a bid to sink his 拢5 billion welfare cuts.
Dozens of Labour MPs have signed an amendment to the Universal Credit and Personal Independence Payment Bill, which is due to be debated in the House of Commons for the first time on July 1.
The amendment sets out a long list of reasons why the Bill should be rejected, including a lack of consultation with disabled people and the Government鈥檚 own assessment that the changes could push an extra 250,000 people into poverty.
If the amendment is selected for debate and if all of the Labour MPs who have signed it were to vote in favour of it, along with opposition parties, it would be enough to kill the Bill.
It represents a major challenge to Sir Keir鈥檚 authority and will send Downing Street scrambling to defuse the situation and keep the Bill alive.
The Government鈥檚 welfare reforms would see more of an emphasis placed on getting people on benefits back into work, with the stated aim of saving 拢5 billion a year by 2030.
Under the proposals in the Bill, ministers will limit eligibility for the personal independence payment which is the main disability payment in England and also limit the sickness-related element of Universal Credit.
But there has been rumbling and growing opposition to the changes from Labour MPs concerned at the impact they could have on some of the most vulnerable people in society.
Ministers have already attempted to soften the impact of the changes but dozens of Labour MPs are still opposed to the Bill.
The amendment has been tabled by Dame Meg Hillier, the chairman of the powerful Liaison Committee, and has been signed by numerous senior backbench figures.
Another nine Labour select committee chairs have also backed the amendment, including Debbie Abrahams from the Work and Pensions Select Committee and Tanmanjeet Singh Dhesi, from the Defence Select Committee.
Other notable Labour figures who have signed the amendment include Diane Abbott, the Mother of the House of Commons, and former leadership contender Rebecca Long-Bailey.
Vicky Foxcroft, the former whip who resigned from the Government last week over the welfare plans, has also signed the amendment.
鈥楥onsult disabled people鈥
The amendment notes the 鈥渘eed for the reform of the social security system鈥 and agrees with the Government鈥檚 鈥減rinciples for providing support to people into work and protecting people who cannot work鈥.
But it states the Bill should be rejected 鈥渂ecause its provisions have not been subject to a formal consultation with disabled people, or co-produced with them, or their carers鈥.
It also states that the Government鈥檚 own impact assessment 鈥渆stimates that 250,000 people will be pushed into poverty as a result of these provisions, including 50,000 children鈥.
A total of 108 MPs have signed the amendment. Ms Abrahams said the MPs 鈥渨ant the Government to listen and to think again on this Bill鈥.
She added: 鈥淲e are being asked to vote for this Bill before disabled people have been consulted, before impact assessments have been conducted and before we have given enough time to some of the Government鈥檚 key policies 鈥 investing in the NHS, to the right to try, and to work coaching 鈥 (to) have been able to bed in.鈥
Liz Kendall, the Work and Pensions Secretary, told a meeting of the Parliamentary Labour Party on Monday evening that the proposed changes were 鈥渞ooted in fairness鈥.
She argued the reforms were about ensuring the survival of the welfare state so there is always a safety net for those who need it.
Ms Kendall added: 鈥淎bove all, they are about our belief that everyone can fulfil their potential and live their hopes and dreams when, collectively, we provide them with real opportunities and support. This is the better future we seek to build for our constituents and our country.鈥