Cabinet ministers have told Liz Truss she must ditch plans to slash benefits - as it was revealed thousands of families in their own constituencies will be hit.
Chancellor Kwasi Kwarteng will announce on October 31 whether the government will stick to its promise to raise payments in line with prices.
The PM is under pressure from members of her top team - including Work and Pensions Secretary Chloe Smith, who has warned failing to match inflation would be a mistake.
Other ministers voicing concerns include Commons Leader Penny Mordaunt, Business Secretary Jacob Rees-Mogg and Wales Secretary Robert Buckland.
At a showdown meeting on Tuesday Ms Truss insisted there are "no easy choices" as she warned the "economic challenge we face is greater” than after the financial crash.
New figures reveal nearly 200 Tory MPs would see more than a fifth of families in their constituencies suffer real-terms benefits cuts if payments do not rise with inflation.
Almost 8,000 people will be hit in Ms Truss’s own backyard if she goes ahead with her plans. Analysis shows 7,908 people in her South West Norfolk seat are claiming Universal Credit.
Tory Cabinet ministers have more than 186,000 people who claim the benefit in their constituencies, according to research by the House of Commons Library.
Ms Smith has 7,497 recipients in her Norwich North patch, while Mr Kwarteng has 6,946 in Spelthorne.
Wendy Chamberlain, the Liberal Democrats ’ work and pensions spokeswoman who uncovered the figures, branded the PM “heartless”.
She said: “Thousands of people in Cabinet members' own constituencies are going to be hit hard by their own actions.
“This government could not be more out of touch with the British people.”
A couple on Universal Credit would face a £290 cut to their income if the government only increases benefits in line with earnings instead of inflation.
Separate research by the Joseph Rowntree Foundation (JRF) found 193 Tory MPs represent areas where at least 20% of working-age families receive means-tested benefits.
Katie Schmuecker of the charity said: "Politicians should think long and hard about the impact of withholding hundreds of pounds from thousands of families in their constituencies when the basic rate of benefits is already at its lowest in real terms for 40 years and prices are sky-high.
"It is unconscionable that the Government should be considering cutting their ability to pay for what they need.
"The Government must realise how catastrophic it would be to refuse to respect their own party's pledge to make sure the value of benefits keeps up with prices.
"The majority of people agree the right thing to do is help the most vulnerable during this extraordinary crisis. The impact will be felt across every constituency in the UK. Now is the time for all MPs to stand up and be counted."
In the Commons, Tory former chief whip Julian Smith warned ministers against balancing forthcoming tax cuts "on the back of the poorest people in our country".
William Hague, the ex-Tory leader, has also joined the disquiet as he told Ms Truss: “Do not keep suggesting that benefits might not be indexed to inflation this winter.”
In an article in The Times, he wrote: “During a cost of living crisis they will have to be, as a matter of social fairness as well as political reality. Refusing to say so will leave ministers with the worst of all worlds: having to come up with the money while being blamed for not wanting to do so.”
