The full roll out of universal credit could see a significant rise in people needing emergency food supplies in Wales, the Trussell Trust has warned.
Director Tony Graham said food banks in Wales were already preparing for more people needing help as the new benefits system is rolled out.
The new system replaces six benefits including housing benefit, unemployment benefits and tax credits.
The DWP said it will help to improve people's lives.
But some claimants who are on universal credit claim long delays in receiving benefits or changes to the money they receive has left them in poverty.
Mr Graham said: "We have seen a 30% increase in food bank usage in areas of universal credit roll-out in England, so we would expect similar sorts of averages to happen here in Wales when universal credit is fully rolled out."
The new system has been fully rolled out in Torfaen and Flintshire, and the rollout has begun in some other Welsh counties including Cardiff. About 30,000 people were already on universal credit in Wales in January this year.
Wales' first Trussell Trust food bank was set up at Festival Church in Ebbw Vale 10 years ago this week.
In its first year, it gave out 76 three-day emergency food supplies but the network has since grown to include 37 food banks and 110 distribution centres across Wales.
Last year, 95,190 three-day supplies were given out to families in crisis across Wales.
Amanda Davies, project manager at Festival Church food bank, said demand had quadrupled since 2008.
Ms Davies said: "We're feeding thousands of people, and that's really sad.
"Some people are really terrified when they come here and yes, we've had families where mothers have fed their children and not themselves for days and days."
- The Trussell Trust says the majority of people need emergency food because of changes or delays to benefit payments, but low wages and rising living costs means many working people also cannot manage
- All food is donated by churches, supermarkets and local people
- Increasingly, food banks are receiving donations of other items, including toiletries, washing powder and pet food
- People in crisis are referred to a food bank by services including charities, social services and GPs
- Supplies can be tailored to individual circumstances, including giving kettle bags - with items such as Pot Noodles - to people who do not have access to cooking facilities other than a kettle
'The fridge is empty'
Paula, 39, is one of those waiting for an emergency food supply for her family.
Although her husband works full time in a factory, she said they had run out of money and there was nothing to eat in the house.
She said: "We just can't keep our heads above water.
"I can't believe I'm here... it's horrible. I don't like to ask people for things but the bills have got to come first and I've got to take care of my family. I've had to borrow money off my brother.
"I have to come to the food bank or we don't eat... the cupboards are empty, the fridge is empty.
"We're struggling, we're a working family, that's what we are, but we're here."
Adrian Curtis, who started the Festival Church food bank in 2008, said: "I knew that Wales was struggling with poverty issues, but the scale of need in Wales has really shocked me over the last 10 years and there are no signs that the need is decreasing.
"It does look like emergency food aid in Wales is going to be needed for some years to come."
The Department for Work and Pensions (DWP) said it hoped universal credit would be completely rolled out to all parts of the UK by 2022.
A spokesman said: "Universal credit lies at the heart of our commitment to help people improve their lives.
"No-one has to wait for their first universal credit payment if they urgently need it, as they can receive up to a 100% advance payment on the very same day they apply."