Work and Pensions Secretary Liz Kendall vowed to defy Labour critics and press ahead with benefit cuts of £5 billion as she warned they were needed to defeat Nigel Farage and Reform at the ballot box. Around 100 Labour MPs, more than a quarter of the total, are reported to have signed a letter urging ministers to scale back changes such as slashing the number receiving Personal Independence Payments, which help disabled people with living costs.

But Ms Kendall said her changes were “crucial to fighting the rise in populist politics”, a reference to the growing popularity of Reform. In a speech hosted by think tank IPPR she warned the current system was “unsustainable”, with the cost of benefits for the disabled and long-term ill set to rise by £8 billion even after the cuts.

Speaking on the same day that Prime Minister Sir Keir Starmer confirmed a partial u-turn over cuts to winter fuel payments, Ms Kendall insisted: “The risk is the welfare state won’t be there for people who really need it in future.”

The package of changes announced in March included increasing Universal Credit for many claimants and ensuring people on disability benefits can look for work without risking losing their payments. However the most controversial change involved removing Personal Independence Payments (PIP) for 800,000 people, including 370,00 current claimants and 430,000 people who will no longer be eligible in the future, each losing an average of £4,500.

Charity Disability Rights UK warned the cuts “are going to lead to deaths” while Help for Heroes said ex-veterans would lose vital support. Labour MPs such as Diane Abbott and Rachael Maskell have publicly condemned the reductions while many others have expressed concern to Ministers in private.

Ms Kendall said nearly one in 10 people of working age are now on a sickness or disability benefit and the number would keep rising. She said: “There are now 1,000 new PIP awards every single day. That’s the equivalent of adding a city the size of Leicester every single year.

“This is not sustainable or fair – for the people who need support and for taxpayers.”

Trying to convince Labour colleagues that the changes are in line with Labour’s traditions, she said: “They follow in the footsteps of the great reforming Labour governments of the past, rooted in our enduring values of fairness, equality and opportunity.”

But Ms Kendall also admitted there was a political motive behind the cuts. She said: “We must deliver real change to fight the rise in support for populists.”

Organisations representing disabled people said they were disappointed that the Government has decided to push ahead. Tom Marsland, head of policy for charity Sense, said: “We agree that the welfare system isn’t currently working for disabled people – but increasing the number of disabled people in poverty will never be the solution.”