Sajid Javid has piled fresh pressure on embattled Prime Minister Liz Truss to abandon plans for a real terms cut to benefits.
The Tory former Chancellor argued that benefits "must stay in line with inflation" - as promised by previous PM Boris Johnson - rather than the lower level of average earnings.
Failure to hike benefits in line with inflation would amount to a real terms cut for some 5.6 million Universal Credit claimants in April.
Ministers are expected to challenge Ms Truss over benefits at a crunch Cabinet meeting on Tuesday, as the Tory rebels turn their focus onto welfare after pressuring the PM into a U-turn on one of her key tax cuts.
It comes as Conservative MPs return to Westminster this week following a torrid party conference in Birmingham, marred by chaos and vicious infighting.
The weakened Prime Minister is mounting a charm offensive to win over angry Tories, with policy lunches with groups of MPs and plans to address the backbench 1922 Committee.
Ms Truss is under intense pressure to drop proposals for below inflation benefit hikes - with ex-Cabinet Minister Mr Javid the latest to break ranks to demand a U-turn.
"People are going through incredibly challenging times," he told BBC Radio 4's Today programme.
"We can all see that in our community. So I personally believe that benefits must stay in line with inflation."
Baroness Philippa Stroud, Tory peer and former advisor to UC architect Iain Duncan Smith, warned "you don't build growth on the back of the poor".
She said: "When we came out of Covid, the £20 uplift (was) removed from this group of people, then there was an opportunity to uprate in line with inflation again, and it was uprated in line at 3%. So, already you've got welfare at historic lows at this moment in time.
"The public knows that. They get this sense that there's something not right in the welfare state at this moment in time.
"So, we would say stop this argument and make sure that we uprate in line with inflation."
Baroness Stroud added: "You don't build growth on the back of the poor. Actually, it's important that at a time when you're going for growth, you really protect the poorest in this country."
Downing Street said the PM was open-minded and listening to Tory concerns about a benefits cut, stressing: “No decision has been made”.
The PM’s official spokesman said a decision would only be made after September’s inflation figures are released on Wednesday 19 October.
“We want to provide that information but we need certain detail before we can make that decision,” he said.
The spokesman said the Work and Pensions Secretary would begin a statutory annual review once those figures roll in. An announcement is normally made in late November with legislation in January, taking effect in April.
But Liz Truss’s spokesman refused to rule out bringing forward the decision earlier, telling journalists: “So obviously, we want to make sure we've got the relevant information, not least the inflation figures before making decisions.
“But clearly we recognise there is a significant level of interest in this, and we will provide any updates as soon as possible.”
He said “no decision has been made”. Asked if the PM is open minded and listening he replied: “Yes”.
Work and Pensions Secretary Chloe Smith was spotted heading into the Treasury for a meeting with Chancellor Kwasi Kwarteng on Monday lunchtime.
A government source suggested it was a routine meeting.
Work and Pensions Minister Victoria Prentis said: "It's obviously a really worrying time for people on benefits because they know that inflation is rising, and they want us to make this decision as soon as we possibly can so that they have the security of knowing how their benefits will be next year."
