Universal Credit, the government's flagship welfare reform, is "a disaster waiting to happen", according to a charity that offers budgeting advice to benefits claimants.
Citizens Advice said claimants transferred to Universal Credit are "more likely to struggle" with priority debts.
The charity said that 79% of the people on Universal Credit which it had advised had such debts - which can include rent and council tax payments - compared to 69% for those receiving benefits under the older system.
The findings were based on an analysis of 52,075 cases, of which 2,151 noted their income was Universal Credit, while 24,002 received "legacy" benefits, between October 2016 and June 2017.
Universal Credit will roll six means-tested working-age benefits into one payment.
Citizens Advice said people it advised who were in receipt of Universal Credit would, on average, appear to have fewer than £4 per month left to pay all their creditors after they have paid essential living costs.
This compared to £16.25 per month for people receiving legacy benefits.
Citizens Advice chief executive Gillian Guy said: "The roll-out of Universal Credit is a disaster waiting to happen.
"While the principles behind Universal Credit are sound, our evidence shows that if the Government continues to take this stubborn approach to the expansion of Universal Credit, it risks pushing thousands of families into a spiral of debt, and placing an even greater strain on public services."
A six-week wait for an initial Universal Credit payment, processing delays within the Department for Work and Pensions (DWP) and the fact some claimants find it difficult to budget were cited by the charity as "causing or exacerbating" debt problems.
But a spokesman for the DWP said: "We are committed to helping people improve their lives and raise their incomes.
Universal Credit does that by providing additional, tailored support not available under the old benefit system, including more help for those in work so they can eventually stop claiming benefits altogether, and under UC people are moving into work faster and staying in work longer than under the previous system."