The government has been accused of ignoring evidence of the distress caused by its welfare reforms following publication of a report which directly links cuts to benefits with a massive rise in food bank use.

The study found that cuts and changes to Britain’s increasingly threadbare social security system are the most common triggers of the acute personal financial crises that drive people to use food banks..

At least half of all food bank users are referred because they are waiting for benefits to be paid, because they have had benefits stopped for alleged breaches of jobcentre rules or because they have been hit by the bedroom tax or the removal of working tax credits, it finds.

The study, the most extensive research of its kind yet carried out in the UK, directly challenges the government’s repeated insistence that there is no link between its welfare reforms and the huge increases in charity food aid.

Watch Britain Isn’t Eating, a microplay about food banks, made by the Guardian and the Royal Court Guardian

The study was commissioned by the Church Of England, the Trussell Trust food bank network, Oxfam and Child Poverty Action Group.

It calls for urgent changes to the “complicated, remote and at times intimidating” social security system to stop people falling into poverty, including a less punitive sanctions system and speedier processing of benefits.

The Department for Work and Pensions (DWP) dismissed the report, claiming the research was inconclusive. “The report itself concludes it can’t prove anything – it uses self-selecting data and recognises there are complex underlying issues. We have a strong safety net in place, spending £94bn a year on working-age benefits, and we provide a wide range of advice and assistance for anyone in need of additional support.”

But the report was welcomed by Jeremy Lefroy, the Conservative MP for Stafford, who hosted its launch at the House of Commons on Wednesday. He said it was an important study that chimed with his experience as an MP in his surgery. He said its recommendations for change, including a review of sanctions policy, would make a practical difference to the lives of many of his distressed constituents.

He added: “There is no doubt from this report that there are certain elements of welfare that make things more difficult, without doubt. These are not the headline things like the benefit cap, but things like sanctions, the smaller things that go below the radar where people cannot get any kind of help.”

The report’s lead researcher, Jane Perry, an independent social research consultant and former DWP official, defended the scope and methodology of the research, which she said accorded with official government social research quality standards.

The bishop of Southwark, Christopher Chessun, said he was disappointed by the DWP’s dismissal of the report, which he described as “an appeal to people of goodwill” to address an important social issue. He urged dialogue with ministers over the problems the report highlights and added: “I think they [the DWP] possibly need to read the report.”

It is understood the DWP was offered a seat on the study’s advisory committee prior to the research but declined. The department was shown a draft copy of the report a month ago but did not raise any objections to its methodology.

In another twist, a DWP minister, Steve Webb, whose officials had apparently agreed for him to respond in person to the report at the launch, pulled out at the last minute, without giving a reason. David McAuley, the chief executive of the Trussell Trust, said he was frustrated that the DWP had not attended, and accused them of not wanting “to hear the story.”

The study says it wanted to examine practical ways of preventing the further expansion of food banks, and warned the government against reliance on charity food to fix holes in the welfare state.

“The promise of a social security safety net that is there to protect people at times of crisis is something that can and must be preserved and protected. Food banks, whilst providing a vital and welcoming lifeline to many, should not become a readily accepted part of that formal provision,” the report says.

There are no official statistics on the use of food banks, but the Trussell Trust, which runs more than 400 food banks in the UK, says 913,138 people were given food parcels by its volunteers in 2013-14 – almost a threefold increase on the previous year, and likely to be a fraction of the total numbers of people experiencing food insecurity.

The research, which examined why people were referred to food banks, combined 40 in-depth interviews with clients at seven UK food banks, analysis of data collected on 900 clients at three of those food banks and a caseload of 178 clients at another.

The authors accept that the research, while wide-ranging, cannot prove definitively why people use food banks or how many use them, but argue that it provides an initial indicator of the scale and prevalence of issues leading people to accept charity food, and call on ministers to commission more authoritative data on food insecurity, as happens in the US and Canada.

The government has struggled to explain why food bank use has risen, though its has denied that welfare cuts are a factor. Lord Freud, the welfare minister, notoriously insisted that demand for food had risen because it was free, while the former education secretary Michael Gove suggested people turned to food aid because they had poor financial management skills.

However, the study found that in most cases people used food banks because they were tipped into financial crisis by events that were outside their control and difficult or impossible to reverse, such as benefit cuts and delays, bereavement or job loss. Most people said they used food banks as a desperate and shaming last resort.

Almost a third of food bank users interviewed for the study who had experienced problems with the benefits system said they had been sanctioned by social security officials and left penniless for weeks on end, while a further third were left unable to put food on the table because of lengthy delays in benefit payments. The report says the current sanctions policy is causing hardship and hunger.

The government has self-imposed targets for processing benefit claims within 16 working days. However, the report says this period is too long a wait without income for vulnerable people, and in practice many claimants wait longer than this. There are concerns that the five-week delay before jobless people can sign on under a future universal credit system will cause hardship.

Formal state crisis support available to people who are left without income because of bureaucratic delays in the processing of benefits was often inadequate or non-existent, the study found. As a result, many people entitled to state help were forced to sell possessions, go without food, or take out expensive credit to buy essentials such as food and rent.

Many people who used food banks lived in or were close to poverty and were attempting to cope with the “ongoing daily grind of living without sufficient income to make ends meet each month”. Many worked, but in jobs that were low-paid and insecure. Often they were also coping with mental and physical ill health and bereavement.

Alison Garnham, the chief executive of Child Poverty Action Group, said: “Food banks have boomed not because they‘re an easy option but because people haven’t got money to eat – often because of problems with claiming and the payment of benefits.

“A delay in a benefits decision or a period pending a review can force hunger and humiliation on families, leaving them no option but the food bank. Rather than protecting these families from poverty at the time when they most need help, the system leaves them with almost nothing to live on.”

McAuley said: “This new evidence brings into sharp focus the uncomfortable reality of what happens when a life shock or benefit problem hits those on low incomes: parents go hungry, stress and anxiety increase and the issue can all too quickly escalate into crippling debt, housing problems and illness.”

The study will feed into an all-party parliamentary group inquiry into hunger and food poverty, chaired by the Labour MP Frank Field, which is expected to report before Christmas.