The U.K. economy may be crawling back to growth, but the number of people relying on food handouts is soaring due to welfare cuts and unemployment.

Charities warned Thursday that as many as 500,000 people may be going hungry as benefits are cut or withheld, food becomes more expensive, jobless rates rise and real incomes are squeezed.

"Cuts to social safety nets have gone too far, leading to destitution, hardship and hunger on a large scale," said Mark Goldring, CEO of Oxfam, one of the charities behind a report entitled "Walking the Breadline." "It is unacceptable that this is happening in the seventh wealthiest nation on the planet."

The U.K. government is cutting spending in a bid to keep its austerity program on track. It has been forced to push back the timetable for reducing government borrowing due to weaker-than-expected growth, but Chancellor George Osborne is determined to stick to the revised targets.

The U.K. economy returned to growth in the first quarter of the year, but is expected to expand by just 0.6% in 2013. The International Monetary Fund last week called for more spending on infrastructure to accelerate the pace of recovery.

Related: EU eases up on austerity, urges reform

One area of spending that has seen the biggest overhaul is welfare. Last month, a number of changes were introduced with a view to saving billions of pounds.

They included a cap on benefits for working-age people, a below-inflation increase for 2013-2014 and a reduction in housing support -- changes that will leave millions of households worse off.

Oxfam, Church Action Poverty and the Trussell Trust -- the U.K.'s biggest provider of food banks -- called on British lawmakers to launch an inquiry into the links between welfare reform and errors made in assessing eligibility, and the rapid growth in the numbers of people unable to feed themselves or their families.

The Trussell Trust says 350,000 people turned to their food banks for help in the last year, almost triple the number who received aid during the previous 12 months.

The charities said the total number of people in the U.K. receiving emergency food aid was likely to be at least 150,000 higher, including those supported by other organizations, and they called on the government to compile a register of referrals to food banks made by social security offices.