Citizens Advice has called for a root and branch overhaul of universal credit, after revealing that half of all claimants who came to it for help managing the new benefit were at risk of being evicted owing to rent arrears and hardship.

Relatively minor changes to the way the benefit operates, announced by ministers in the 2017 budget after coming under intense pressure from campaigners, have “only made a dent in the problem rather than fixed it”, the charity said.

The minimum five-week wait for a first benefit payment left nearly half of claimants it advised unable to pay household bills, or forced them to go without essentials such as food or heating, it said, while 54% had to borrow cash from family and friends to stay afloat.

“Half the people we help with universal credit are still struggling to keep a roof over their heads while they wait for their first payment,” said Gillian Guy, the chief executive of Citizens Advice.

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She added: “Changes to the waiting period for first payment have improved things for many people, but our evidence shows they don’t go far enough. Universal Credit must continue to be reformed so it works for all claimants and leaves people with enough money to live on.”

The charity said rent arrears were more common among its clients on universal credit compared with those on the benefits it replaces, as was debt. Although the changes had helped some claimants to cope, “too many people on universal credit are still struggling to manage their money”.

The changes announced in the 2017 budget include a shortened wait for a first payment from 42 days to 35, two weeks’ extra housing benefit, and more generous advance payments to help people manage the wait. Further changes flagged in the 2018 budget will come in over the next two years.

The charity says that although fixing fundamental design and reliability issues in universal credit are crucial, the overriding problem is that payments are too low because of the benefit freeze and housing benefit cuts.

“The people we see on universal credit often struggle because the level of income they live on leaves no budget for any unexpected expenses or income shocks. Some simply do not have enough money to live on,” it says in a report.

“Fixing issues in the design and delivery of universal credit can help with the five-week wait and ongoing budget issues, but people need to be paid reliably at a level that gives them enough to meet essential living costs.”

The work and pensions secretary, Amber Rudd, signalled last month that she would consider further policy changes and rollout delays to restore public confidence in universal credit, telling MPs her priority was to make it safe for vulnerable claimants.

A Department for Work and Pensions survey of universal credit claimants published last week found one in five were not satisfied with their experience of the new benefit – and one in 10 reported being “very dissatisfied”.

A DWP spokesperson said: “Most people on universal credit are happy managing their money, but budgeting support is available for anyone who needs extra help. Many people join Universal Credit with existing rent arrears, but this falls by a third after four months.

“We will continue to work closely with Citizens Advice and other stakeholders to develop our approach in order to provide the best possible support for all of our claimants.”