Thousands of vulnerable people on low incomes – particularly those with mental illness – are at risk of destitution because they do not have the skills or support to apply for and maintain a universal credit benefit claim, the Salvation Army has warned.

The Christian church and charity said there was “overwhelming evidence” that many people found it a struggle to engage with the mainly digital benefit, leaving them unable to pay rent or buy food and effectively locking them out of employment support.

Quick guide What is universal credit and what are the problems? Show Hide What is universal credit? Universal credit (UC) is the supposed flagship reform of the benefits system, rolling together six benefits into one, online-only system. The theoretical aim, for which there was general support across the political spectrum, was to simplify the system and increase the incentives for people to move off benefits into work. About 2 million people are currently in receipt of UC. More than 6 million will be on the benefit by the time it is fully rolled out. How long has it been around? The project was legislated for in 2011 under the auspices of its most vocal champion, Conservative MP Iain Duncan Smith. The plan was to roll it out by 2017. However, a series of management failures, expensive IT blunders and design faults mean it is now seven years behind schedule, and rollout will not be complete until 2024. The government admitted that the delay was caused in part by claimants being too scared to sign up to the new benefit. What is the biggest problem? The original design set out a minimum 42-day wait for a first payment to claimants when they moved to UC (in practice this is often up to 60 days). After sustained pressure, the government announced in the autumn 2017 budget that the wait would be reduced to 35 days from February 2018. This will partially mitigate the impact on many claimants of having no income for six weeks. The wait has led to rent arrears and evictions, hunger (food banks in UC areas report notable increases in referrals), use of expensive credit and mental distress. Ministers have expanded the availability of hardship loans (now repayable over a year) to help new claimants while they wait for payment. Housing benefit will now continue for an extra two weeks after the start of a UC claim. However, critics say the five-week wait is still too long and want it reduced to two or three weeks. Are there other problems? Plenty. Multibillion-pound cuts to work allowances imposed by the former chancellor George Osborne mean UC is far less generous than originally envisaged. According to the Resolution Foundation thinktank, about 2.5m low-income working households will be more than £1,000 a year worse off when they move to UC, reducing work incentives.

Landlords are worried that the level of rent arrears accrued by tenants on UC could lead to a rise in evictions. It's also not very user-friendly: claimants complain the system is complex, unreliable and difficult to manage, particularly if you have no internet access.

And there is concern that UC cannot deliver key promises: a critical study found it does not deliver savings, cannot prove it gets more people into work, and has plunged vulnerable claimants into hardship.

It called on the government to increase the level of support to make it simpler for vulnerable people to make a claim before the next phase of the universal credit programme later this year, when about 750,000 ill and disabled benefit claimants start to be moved on to the benefit.

“Rolling out universal credit in its current form will steamroll vulnerable people into poverty, but the government has time to turn this around by accepting our recommendations and making it easier to apply,” said Rebecca Keating, the Salvation Army’s employment director said.

There is concern among campaigners and even the government’s own social security advisers that the government has not done enough to ensure vulnerable claimants do not fall out of the system altogether when they are transferred to universal credit in the process called managed migration, which is due to start in late autumn.

Claimants with mental health problems, learning disabilities and physical disabilities, as well as homeless people were especially at risk, it said. Some lacked computer skills, or could not access the internet because they did not own a smart phone or because there was no public computer nearby.

The charity cited the case of Daniel, a young man with dyslexia, who struggled to read and write. He had his benefits stopped and ended up homeless after putting the wrong phone number on his online form and missing a text appointment with the job centre.

Although Daniel was allocated a key worker he said the extent of his dyslexia was never fully understood. “I needed things explained to me properly and I couldn’t read all the leaflets he was giving me to go away with. That went on for six months,” he said.

The government’s own figures showed one in five online claims were dropped before they were completed, the Salvation Army said, suggesting 20% of people who were eligible for universal credit because of low pay or unemployment were effectively dropping out of the benefit system.

Some of those who managed to sign up to universal credit subsequently dropped out after being sanctioned for failing to keep up with its tough conditionality requirements, such as 35 hours a week of online job searches. These rules, known as claimant commitments, often did not take a person’s vulnerabilities into account

About 85% of those interviewed reported problems signing up to universal credit. Of those, 42% said mental ill health was a barrier. The charity said that overstretched job centres were failing to identify vulnerable people and offer them appropriate support, while government help to claim programmes could not meet demand.

The charity insisted it wanted universal credit to be a success, but it had a duty to point out where it was going wrong. “This is not just another paper for decision-makers to ignore and label as scaremongering,” it said. “These are people’s lives.

“We are not saying ‘bin universal credit, it’s no good’; this is about us wanting to make the system work,” said Keating. “Digital works for a lot of people but there is a significant group of people that it is not working for.”

The Department for Work and Pensions said that although 98% of people make their claim for universal credit online, people who struggled with computers were able to make a claim in person or over the phone. Extra support was available through the Help to Claim service, delivered by Citizens Advice.

A DWP spokesperson said: “Jobcentres across the UK have staff trained in supporting vulnerable people and tailor people’s benefit claims to match their circumstances, including taking into account mental health, issues with domestic abuse and homelessness.”

The Salvation Army’s research was based on interviews between March and June 2019 with 160 people across England and Wales who were out of work and looking for a job and had signed up to the charity’s Employment Plus programme.