By Ian Woods, Senior Correspondent
The Prime Minister has made a secret visit to his local food bank, after criticism that Downing Street does not understand the increasing role they are playing in 'Austerity Britain'.
Mr Cameron visited the charity, which operates out of a church hall in his constituency in Oxfordshire, and spoke to volunteers who supply up to 10 families each week with emergency food parcels.
Nationally, the use of food banks has grown, with the largest operator, the Trussell Trust, now running 310 centres. The trust helped 260,000 people in the past year, an increase of 60,000 on the year before.
The Witney food bank was set up by Jo Cypher, who told Sky News: "We've had people coming in saying 'we've had a choice this week, either we buy electric, we buy gas, we pay bills, or we eat'."
Her colleague Julie Walker-Lock said they were helping a variety of people. "We're seeing from the elderly down to the families with young children. We've had a barrister in - he'd been looking after his wife and she'd passed away and he'd lost everything, and he came here, and we helped him out."
Melody Hopkins is one of the those who has used the Witney food bank. She told Sky News she was a victim of domestic violence, and then lost her job as a carer for disabled people.
More and more people are relying on food banks
Despite receiving benefits and child tax credits, she said she struggles to pay rising food and heating bills, and care for her eight-year-old son Toby who requires daily medication for Attention Deficit and Hyperactivity Disorder. She found it difficult to make the transition from wage earner to welfare recipient.
"My wages had stopped, so I had to wait for the benefits to kick in. We were desperate. We didn't have any food. At one point I had a fiver, in my back pocket, to just go and get some food.
"It's sad to think that I used to work, I used to do three meals a day, it was great, and now it's come down to one meal a day, because Toby gets free lunch at school. So I haven't eaten today - I'll eat later with him. I have gone without because Toby comes first ... it's sad when I can't give Toby the food he wants."
Difficulties in finding childcare after school for a child with special needs mean Ms Hopkins cannot get a full-time job, so she does voluntary work instead.
"I don't want to be on benefits. I want to go back to work and do a job. I've always worked. This is the only one or two years I haven't had a job," she said.
The food bank in Witney is housed in a church hall
Ms Hopkins added that she shops for clothes once a year, gets furniture from charity shops and avoids big supermarkets.
"Every aisle is temptation, you need to go around those shops and not even look at the prices. I can't do that. I go in with a basket and it's the bare essentials - can we make tea out of what we've got? And you see people walking out with big trolleys and you think OK, I haven't got that, we've got what we need and we will go," she explained.
To help as many people as possible, and to avoid dependency, food banks permit only three visits per year, and recipients have to have been referred by a charity or other agency. GPs are now prescribing food as well as medicine to patients.
Dr Raj Kohli, from the Deer Park Medical Centre in Witney, told Sky News: "I do come across families who are struggling to appropriately feed their children. Particularly with fresh fruit and vegetables, it's expensive.
"We're not necessarily seeing the physical effects of malnutrition at this stage, but they are struggling. We need to look at their immediate needs, and a food bank can help their immediate needs."
Food bank user Melody Hopkins prepares a meal
Witney is not the sort of place you might expect to find poverty. The Cotswolds town has only 909 people claiming Jobseeker's Allowance and its unemployment rate is less than half of the national average.
But there are enough people struggling to make ends meet to mean the food bank has become a vital resource. Even the local Brownie pack saved loose change and then put all their money together to buy tins of food to give to the poor. Shoppers and supermarkets both donate groceries which can be used in food parcels.
The volunteers at the Witney food bank were sworn to secrecy about the Prime Minister's visit, and no cameras were present.
But they said that he listened to their comments about why the food bank was needed and their fears that changes to the benefits system in April could bring a fresh influx of people who find it hard to pay their bills.
Previously, a Downing Street spokesperson has said: "Benefit levels are set at a level where people can afford to eat. If people have short-term shortages, where they feel they need a bit of extra food, then of course food banks are the right place for that. But benefits are not set at such a low level that people can't eat."
Affluent Witney is not necessarily where you would expect to find poverty
Volunteer Julie Walker-Lock told Sky News: "I think that was a very ill-informed statement they made. There is a genuine need for us to be here."
Ms Cypher said: "We were glad he came, because I think he was blind to the fact that, like everybody else, supposedly Witney is very rich. It's actually quite the opposite. It's not.
"I think he went away with a better understanding of how the system works and why we're here. I'm hoping that we went away with some of those thoughts, and he will act on them."
For those who use the food banks, items like pasta and tins of soups can be an essential part of their diet. But sometimes it's having an occasional treat which can lift people out of depression. An unexpected Christmas hamper made all the difference to Ms Hopkins and her son.
"To everybody else they're not luxuries, but to me and my son they were luxuries. They were things I wanted to buy but couldn't afford to buy, and it brought some tears to our eyes.
"Christmas Day we just had a standard chicken. Most people have turkey, we didn't, we had tinned veg. I mean, it was OK, but we had the little extras like a cracker each, and mince pies. My son was like 'I got sweeties' and I actually wrapped them up and put them in his stocking - that's how important it is to us," she said.
The Government is set to announce childcare reforms 
