Gordon Brown has warned of a “national uprising” if the Government opts not to increase benefits in line with inflation.

The former Labour prime minister became the latest political heavyweight to weigh in on the row over the uprating of benefits, an issue that has prompted backbench revolts at the Conservative Party conference and prompted signs of splits even within the Truss administration.

Appearing on BBC Radio 4’s Today programme, Mr Brown said it would be “immoral” not to increase benefits alongside inflation, which has soared in recent months to levels unseen in generations.

Liz Truss and Chancellor Kwasi Kwarteng have so far not ruled out such a real-terms cut to benefits, as the pair seek out ways to shave billions off Government spending following last month’s tax-cutting mini-budget.

Work and Pensions Secretary Chloe Smith reiterated the Government line on Wednesday, saying a statutory review takes place in October and “can’t be done yet because I need to use the latest data”.

Mr Brown said not raising benefits in line with inflation would be “unfair” and “unequal”.

“It’s divisive because we’re not in this together any more. It’s anti-work because 40% of those who would suffer are people on low pay in work. It’s anti-family because five million children would be in poverty.

“And I think most of all, it’s immoral. It’s asking the poor to bear the burden for the crisis that we face in this country and for mistakes that other people have made, and it’s a scar on the soul of our country, it’s a stain on our conscience.”

Mr Brown said the majority of the public would be against it, warning: “There will be a national uprising if this goes ahead because it is nothing to do with making the growth policies of the Government work, it is simply making the poor pay the price.”

The former Labour leader also hit out at the mini-budget, as he warned that the country could expect further crises to come.

“If you look at that budget, irrespective of removing the top rate tax cut from 45p to 40p, there are billions of pounds that were given away to those who are already wealthy that could be used to pay for the benefits and to stop the health service being starved of resources that it needs.”

“In the long run, what you cannot do is build a growth strategy either around penalising the poor, or around simply giving tax cuts to those who are richest,” he told the programme.

On Tuesday, Cabinet Minister Penny Mordaunt became the most high-profile member of the Truss top team to back calls from Tory MPs to uprate benefits with inflation, straining the limits of Cabinet collective responsibility.

Ms Truss ruled out sacking her former leadership rival for speaking out on the issue, one of several to dominate the conference as MPs piled pressure on the Chancellor after successfully forcing a U-turn on plans to scrap the 45p top rate of tax.

Asked on the BBC’s Politics Live programme on Wednesday whether benefits should rise with inflation, Ms Smith said: “There is a statutory process here. I, as Secretary of State for Work and Pensions, undertake an annual review of benefits and pensions. That happens in late October. It doesn’t happen yet.”

Mr Brown, among the longest-serving of British chancellors, also warned that that he did not think the “crisis is over” in the markets.

“You’ve got problems with inflation, potentially problems with liquidity and solvency amongst companies. And you’ve got the potential for markets to be dysfunctional.

“And I would be worried about the shadow banking – that’s the non-bank financial sector in this country.

“And I would be very careful if I was the Bank of England and make sure that the supervision of that part of the economy is tightened up, because I do fear that, as inflation hits and interest rates rise, there will be a number of companies and a number of organisations that will be in grave difficulty.

“So I don’t think this crisis is over because the pension funds have been rescued last week.”