The likelihood of having trouble putting food on the table has almost doubled among those with low incomes in most of the UK since 2004, researchers have found.

The study reveals that one in five adults across England, Wales and Northern Ireland experienced some level of food insecurity in 2016.

It also shows that vulnerability to food insecurity has increased in recent years among low-income adults, in particular those with disabilities. While the study does not show what is behind this rise, the team say welfare reform is a likely culprit.

“When we look again at who are the groups that are standing out here, it just seems that it is probably not coincidence that it is people who have been affected by the major changes to social security happening over this period,” said Dr Rachel Loopstra, the first author of the research from King’s College London, adding that while factors including rising food prices might also play a role, they could not explain why the rise is steeper for people with disabilities.

In April, the Trussell Trust revealed that it had given out a record 1.6m emergency food parcels last year, but the latest study suggests this accounts for only a small fraction of adults experiencing difficulties feeding themselves and their families.

Writing in the Journal of Epidemiology and Community Health, researchers from the UK and Canada report that they scrutinised the results from a 2016 survey of more than 3,000 adults aged 16 or older in England, Wales and Northern Ireland.

The results reveal that 21% of adults – more than 10 million people – experienced food insecurity to some degree.

After taking into account other factors, the team found that the people with a greater chance of such worries included non-white adults, those with children in the household, those with a low level of education or a low income, those living with a disability, and those who were unemployed. Those under 35 had a greater likelihood of experiencing some level of food insecurity compared with middle-aged people.

About 3% of adults were found to experience severe food insecurity – such as actual hunger. “That’s when we see only three characteristics really stick out: disability, unemployment and being in the lowest income group,” said Loopstra.

The team then compared the data for about 240 low-income adults from the survey with data from more than 900 adults with similar characteristics, collected as part of a UK study of very deprived households in 2004.

They found the probability of experiencing food insecurity has almost doubled in recent years among those with low incomes, rising from 28% in 2004 to 46% in 2016. Those living with disabilities or illness experienced a particularly drastic increase, with the probability of food insecurity rising from 28% to 54% over the period.

“In contrast, we didn’t see any rise amongst people who were retired, and that is the group that has generally been more protected from welfare reform,” said Loopstra.

The team say this research cannot show whether the actual numbers of people experiencing food insecurity or going hungry have increased, while the figure for rising food insecurity was based on comparing particular low-income individuals and therefore might not apply across the board. Exact data regarding income and nature of employment was also lacking.

However, they say the findings reveal people with low incomes are increasingly vulnerable to difficulties feeding themselves and their families.

Danny Dorling, a professor of human geography at the University of Oxford who was not involved in the study, said the findings of the research were robust but conservative.

“Given current social trends and government policies we should expect the figures to have worsened since 2016,” he said. “If that is the case then a majority of the poorest families with children in Britain today can no longer afford to buy enough for them and their children to eat adequately.”

A government spokesperson said other data had shown an overall fall in food insecurity over the last few years, but that more needed to be done to tackle the problem.

Chris Goulden, the deputy director of evidence and impact for the Joseph Rowntree Foundation, said rising food bank use showed many people in the UK cannot afford to eat..

“Unless we tackle the underlying causes that lock people into poverty, such as low pay, high housing costs and a social security system that isn’t protecting people from harm, then hunger and destitution will inevitably continue,” he said.