Food banks in some of the poorest areas are preparing for a big rise in demand when universal credit is rolled out by calling for more donations and volunteers, and stockpiling essential supplies.

Volunteers have told the Observer they are concerned about how their communities will cope this winter. In areas where the new benefit has been in place for months, the pressure on food banks has increased. Under the new system, people are made to wait for over a month to receive the benefit. When universal credit is paid out, it is often given as a lump sum, which many find difficult to budget.

The Trussell Trust, which operates 428 food banks, reported in April that its facilities were four times busier in areas where the new credit had been in place for 12 months or more compared with those where it had been introduced more recently.

Blackpool, the Isle of Anglesey, Milton Keynes and parts of Liverpool and Glasgow will become some of the last places to introduce universal credit in the coming weeks.

Roy Fyles, who supervises the Anglesey food bank, said he was not looking forward to its arrival on 5 December. “Even if there are only a few new claimants between now and Christmas, they will not get any money, unless they request an advance, until the new year,” he said. “We’re talking five weeks.”

In nearby Flintshire, the credit piled a lot of pressure on food banks when it was brought in 20 months ago. “We are hoping that, because we’re only a small island, we’ll have fewer problems,” Fyles said. Already, the number of packages his food bank delivers has gone up by a third in the past few months. “We’re preparing by trying to get more volunteers and collecting food for Christmas hampers.”

In the London borough of Brent, Mohammed Mamdani, director of the Sufra NW London food bank, is stockpiling supplies in anticipation of the havoc he thinks universal credit – which was introduced there on 21 November – is about to bring. He is collecting toiletries, cleaning materials and other less-commonly donated items such as tinned fruit and vegetables.

“Food banks across the UK are calling to tell us that they have suffered significantly, because of increases in demand,” Mamdani said. “They’ve suggested that we need to be more prepared than they were.”

At Milton Keynes food bank, John Marshall, the manager, said he had had no support, except from the public, to help deal with the potentially higher burden. “We thought the cavalry might be coming over the hill but there doesn’t seem to be one.” He hopes that the food bank’s full warehouse will last it through the Christmas season, and expects that any pressure points will appear in February or March.

In Blackpool, Bev Taylor manages the Bridge Project, which is part of the Salvation Army and helps people in crisis. “We are in one of the most deprived areas of the country,” she said. “I am concerned about much bigger demand. We are going to run out of sleeping bags and blankets if problems persist, and we are going to have to put out a call for more donations over the Christmas period.”

Landlords with whom the Bridge Project has worked for years to house vulnerable people were now refusing to take universal credit claimants because their finances were so unstable, Taylor said. “We are now constantly working in homelessness prevention because of UC.”

Taylor added that while the new monthly payment “might work for some families that can budget their own finances, it does not work for people coming into our centre. Giving a lump sum that includes rent and living expenses to people suffering from an addiction is not a good mix.”

The full rollout of universal credit for existing welfare claimants has been delayed repeatedly. It is now set to begin for small numbers of people in early 2019, and will not be fully operational until 2023.

Emma Revie, the chief executive of the Trussell Trust, said: “We’re seeing soaring levels of need at food banks. The time to act is now. If the five-week wait isn’t reduced, the only way to stop even more people being forced to food banks this winter will be to pause all new claims to universal credit. We have to make sure our benefits system can protect people from hunger.”