The “scandalous” prosecution of unpaid carers uncovered by the Guardian must end now and an inquiry must be launched immediately, Rishi Sunak has been told. The pressure on the prime minister grew as three former work and pension secretaries and Labour demanded to know why thousands of people who care for their loved ones have been hounded for thousands of pounds – and in some cases convicted – after unwittingly breaching earnings rules by just a few pounds a week. Unpaid carers have described being plunged into debt, given criminal records and forced to sell their homes when chased by the Department for Work and Pensions (DWP) over “honest mistakes” that officials could have spotted years earlier. Now three former secretaries of state for work and pensions – the former Tory leader Iain Duncan Smith, and Labour’s Alan Johnson and David Blunkett – have joined the growing chorus of anger after dozens of unpaid carers came forward to describe how they had been pushed further into hardship by the DWP’s actions. Blunkett said: “It’s a no-brainer that the government should take an urgent look at why the system is hitting those on the very margins and who are providing much-needed support to loved ones.” The welfare system was “broken”, he said, comparing the “persecution of carers” with the UK’s failure to tackle the tens of billions of pounds lost each year due to tax fraud. Johnson said the DWP had an obligation to “tread softly” with unpaid carers, who save the UK £160bn a year and lead incredibly stressful lives with often very little income. He said the DWP “need[s] to ascertain if overpayments have been made before making any decisions on repayment”, and added: “I doubt if threats of legal proceedings are appropriate in this situation.” Caroline Dinenage, the chair of the carers all-party parliamentary group and a Conservative MP, said: “The numbers of those falling foul of carer’s allowance overpayment suggests that the issue needs the government’s attention. This is especially true for cases where DWP does not inform individuals promptly of the situation, allowing months (and sometimes years) of overpayment to accrue.” Alison McGovern, the acting shadow work and pensions secretary, on Friday demanded an urgent investigation as the scandal continued to grow. She said: “It is outrageous that the Tories have failed to use real-time information to stop overpayment. That’s a waste of money and very stressful for the carers concerned. The government need to urgently investigate why this has happened and to outline what steps they are taking to rectify it – including publishing their report on this issue in full.” The Guardian can reveal that MPs are planning to question the welfare minister, Mims Davies, on the issue of carer’s allowance overpayments when she gives evidence to the work and pensions committee later this month. Four MPs on the committee, including the chair, Stephen Timms, have raised concerns about the DWP’s actions after the reporting by the Guardian this week. Timms said MPs would question Davies on the issue when she appears before the committee on 24 April. “Clearly something has gone wrong on this,” he said. Nigel Mills, a Conservative MP on the committee, said it was clear that unpaid carers “shouldn’t face any penalties” when the blame lay with the DWP for failing to stop the overpayments from mounting. He said: “By definition, carers on this allowance can’t earn large amounts of money, so there’s no real way for them to pay this back. Some of them are living on less than those on state benefits. It’s a really tight situation for people.” Ministers are under pressure to explain why the DWP is still failing to spot overpayments much sooner, despite promising five years ago to tackle the issue after being heavily criticised over its treatment of thousands of carers. A report by the work and pensions committee in 2019 accused the DWP of “bullying and harassing” those who had been overpaid carer’s allowance, worth £81.90 a week – the smallest benefit of its kind. It blamed DWP administrative failures for not spotting the infringements earlier, and rigid rules that “set carers up for a fall”. Although at the time ministers promised to address the problem of overpayments through new data-matching technology, vast numbers of carers are still falling foul of the system, being forced to repay large sums, and in some cases having their assets seized by DWP fraud investigators. Debbie Abrahams, a Labour MP on the committee, on Friday called the DWP’s approach “simply vindictive” and said that the committee was keen to interrogate ministers about “the inadequate support carers receive”. Managers in the DWP have tried to boost staff morale in the wake of the carer’s allowance saga, which has been described by the centre-right Centre for Social Justice thinktank as a “scandalous miscarriage of justice” and by a former senior Labour aide as “the cruellest benefits crackdown we’ve seen yet”. In a message to DWP staff this week, a senior official described the media coverage as “one-sided” and sought to defend those handling carer’s allowance claims, saying the controversy was “aimed more at how DWP recover debt, so that is not even aimed at carer’s processes anyway”. A DWP spokesperson said a carer’s allowance had increased by about £1,500 an unpaid carer since 2010. This works out as a rise of about £28 a week, or slightly higher than the rate of inflation. “We are committed to fairness in the welfare system, with safeguards in place for managing repayments, while protecting the public purse,” they said. “Claimants have a responsibility to inform DWP of any changes in their circumstances that could impact their award, and it is right that we recover taxpayers’ money when this has not occurred.”