Thousands of cancer patients are being put at risk by Universal Credit.
They face having no cash to buy food or pay for heating under the system.
Even those with a terminal diagnosis who are at the end of their lives are being denied the financial support they need, a charity warns.
Alarmingly, 26,000 cancer patients face hardship if the "failing" new benefits system continues to be rolled out, Macmillan Cancer Support says.
It warns that people with cancer are being forced to wait five weeks to receive urgent financial support, even at the end of their lives, putting them at risk of hardship, stress and anxiety.
Strict new rules also mean cancer patients are having to apply online, which is difficult in hospital or without a computer, or travel to Job Centres to do so, where there is risk of infection.
The devastating report comes as The Mirror is campaigning to halt the rollout of Universal Credit and replace it with a fairer system.
More than 41,000 have signed our petition.
Macmillan Cancer Support chief executive Lynda Thomas said: “People with cancer should be able to focus their energy on their health, not worrying about how to make ends meet when they are too unwell to work.
"It is unacceptable to force patients to risk infection at Job Centres, log onto computers from hospital and wait more than a month for vital financial support, even at the end of their lives.
"The system is failing people with cancer and we urge the Government to fix this benefit, before tens of thousands more vulnerable people are put at risk of hardship."
Universal Credit - which will merge six benefits into one payment - was supposed to be up and running by April 2017, but is now not expected to be fully operational until December 2023.
Macmillan say that current Universal Credit rules mean that cancer patients face a five-week wait before they receive any money at all.
The duration applies to those with a terminal diagnosis, with a fast track process for people with less than six months to live removed.
It means dying patients at the end of their lives face a longer wait for vital financial support.
Grandmother Angela Raine was forced to give up her 13-year job in a pharmacy when she was diagnosed with incurable breast cancer last year and became too unwell to work.
The married 55-year-old, of Stanley, County Durham, said: “Trying to apply for benefits has been a complete nightmare. I can’t explain quite how stressful it is - I want to cry just thinking about it.
"I was trying to cope with being told I may die and yet at the same time I’m having to fight to just get a little money, so that we can survive."
She added: "Navigating the system is a nightmare, that’s quite honestly the only way I can describe it. The forms are all so confusing and difficult. It’s as if they do that to stop you from applying.
"I don’t have an email address because I don’t use the computer, but without an email address, you can’t apply or fill in the form. The whole system is utterly inflexible and doesn’t take into account individual circumstances."
Benefits adviser Elaine Donnelly said: "I never thought we'd have to give out food bank vouchers to people with cancer. Some days the staff are in tears, struggling to believe what the system is doing to people who are very ill.
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The Mirror are demanding a halt to the expansion of Universal Credit and for a review to take place.
We say there are three options:
Redesign UC to be fit for purpose
Axe it in favour of the old system if UC is unfixable
Introduce a brand new system
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"We've had people die before they got their benefits. The system just doesn't work."
Cancer can affect someone’s ability to work. As a result, cancer costs an average of £570 a month for the majority (83%) of patients, due to lost income and extra outgoings, such as increased household bills due to feeling the cold more.
More than a quarter of those diagnosed have no savings to fall back onand the welfare system provides a vital safety net to help people manage the impact of their illness.
But the report by Macmillan warns that any delays or obstacles to receiving financial support can be a source of extreme worry and financial hardship at an already difficult time.
The charity demanded the UK Government to fix the existing issues with the system, including challenges of applying for those who are undergoing treatment.