A "shocking" 1.25 million people in the UK were classed as destitute last year, including 300,000 children, according to a new study.
Research by the Joseph Rowntree Foundation found that four out of five of those people were born in the UK, while young, single people, particularly men, were more likely to be destitute, although considerable numbers of families were also counted.
Most people had been living in poverty before tipping into destitution, with the most common causes including the extra costs of ill health and disability, the high costs of housing and other essential bills, unemployment and a financial shock like a benefit sanction or delay.
Julia Unwin, chief executive of the Joseph Rowntree Foundation, said: "There are a shocking number of people in the UK living in destitution. It is simply unacceptable to see such levels of severe poverty in our country in the 21st century.
"Governments of all stripes have failed to protect people at the bottom of the income scale from the effects of severe poverty, leaving many unable to feed, clothe or house themselves and their families.
"Tackling the many causes of destitution is difficult. Many people affected are living on a very low income before they are no longer able to make their incomes stretch, or a financial shock like a benefit delay or family breakdown pushes them over the edge into destitution.
"We have to tackle these root causes. Government, businesses and communities need to work together to provide better emergency support, make basic essentials more affordable and create better jobs if we are to end destitution in the UK."
The report said destitution was the most severe form of poverty, meaning someone cannot afford the basic essentials they need to eat, keep clean and stay warm and dry.
The total number of destitute people in the UK is not currently measured by the Government, the report noted.
The definition of destitution was said to be when someone lacked two or more basic essentials in one month, had slept rough, had one or no meals a day for two or more days, been unable to heat or to light their home for five or more days, gone without weather-appropriate clothes or gone without basic toiletries.
Researchers found that 1,252,000 people, including 312,000 children, were destitute at some point in 2015.
Professor Suzanne Fitzpatrick, of Edinburgh-based Heriot Watt University, one of the authors of the report, said: "Destitution takes a huge toll on people's mental and physical health and wellbeing. The people we spoke to told us they felt humiliated that they couldn't afford basic essentials without help. Many said that this affected their relationships and left them socially isolated.
"This report has shown that destitution is intrinsically linked to long-term poverty, with many people forced into destitution by high costs, unaffordable bills or a financial shock such as a benefit sanction or delay.
"More co-ordinated debt-collection practices, particularly from DWP, local councils and utility companies, could help to avoid small debts tipping people into destitution."
A Government spokesman said: "The truth is that relative poverty is at the lowest level since the 1980s and the number of children in poverty has fallen by 300,000 since 2010.
"This report ignores a number of measures we've brought in to improve life chances, including the national living wage, the extension of free childcare to 30 hours and increases to the personal allowance.
"We also continue to spend £80 billion on working age benefits to ensure a strong safety net for those who need it most."
Rhiannon Sims of Citizens Advice Scotland said: "These figures show the scale of destitution in the UK, and are a sobering reminder that not enough is being done to prevent people from experiencing periods of no income, or to provide adequate support when people are faced with a crisis.
"Our evidence shows us that many people have no resilience to income shocks, and it only takes a delayed benefit payment or the loss of a shift at work to push someone into a situation in which they cannot afford basic essentials - food, shelter and warmth."
The chief executive of Child Poverty Action Group, Alison Garnham, said: "To have 300,000 children going without absolute essentials - and many, many more, even in working families, unable to participate in ordinary life - is shocking evidence of UK complacency on poverty.
"The new Work and Pensions Secretary has the opportunity to make good on the Government's promise to mount an assault on poverty. The first moves in that assault should be to enact a number of technical fixes to the problems in benefits administration that often act as the immediate triggers for destitution, alongside policies to re-invest in Universal Credit and to tackle the high housing and childcare costs that leave parents so vulnerable."