The number of people relying on food banks to survive has tripled over the last year, according to new figures.
The Trussell Trust, which runs 400 food banks across the UK, said it handed out supplies to more than 350,000 people between April and September this year.
A third of those being helped were children, and a third needed food following a delay in the payment of benefits.
A cross-party group of MPs has been set up to investigate the surge in demand.
The Labour MP Frank Field, appointed by David Cameron as the government's poverty advisor, will head up the committee along with Conservative Laura Sandys.
Mr Field said they would investigate the impact of benefit of cuts, low wages and high food prices.
The Trussell Trust said the problem was so severe that some people using food banks have started to hand back items that need cooking, as they cannot afford to use the energy.
The Trust is calling for a public enquiry into why so many people are having difficulty feeding themselves.
"The level of food poverty in the UK is not acceptable," said Chris Mould, the Trust's executive chairman.
"It's scandalous, and it is causing deep distress to thousands of people, " he added.
Food banks work through a system of referrals.
Professionals including doctors and social workers hand out vouchers, which in the first instance can be exchanged for three days' worth of emergency food.
The Trust said that the problem of hunger in the UK is getting worse.
Rising living costs and stagnant wages are forcing more people to live on a "financial knife edge", it said.
It also forecast that rising energy prices this winter are likely to see more people "choosing between heating and eating."
It admits that one reason for the rise in the numbers is that there are twice as many food banks in existence as last year.
But the Trust says the number of people using them has still tripled, and that even the well-established food banks are reporting significant rises in their use.
It claims that problems with benefit payments is a major factor.
"We're talking about mums not eating for days because they've been sanctioned for seemingly illogical reasons," said Mr Mould.
"Or people leaving hospital after a major operation to find that their benefits have been stopped or delayed," he added.
However the government has taken issue with the report.
"The Trussell Trust itself says it is opening three new food banks every week, so it's not surprising more people are using them," said a government spokesperson.
On the matter of benefit payments, the Department for Work and Pensions (DWP) said that there was "no robust evidence that welfare reforms are linked to increased use of food banks".
It also said that benefit processing times have steadily improved over the past five years, with 90% now being paid within 16 days.
There was further evidence of increased demand for food hand-outs from FareShare, an organisation which distributes supplies to more than 1000 charities across the UK.
It said requests for its services had risen by 15% over the last year.
The supermarket giant Tesco has now agreed to donate all its fresh surplus food to FareShare, so providing 7 million meals a year to those who need them.