Around 1.2million people fear they will be forced to skip meals if the Government presses on with plans to cut Universal Credit payments this October.
The Trussell Trust, the UK's biggest food bank charity, said a further 1.3m people fear being unable to heat their homes if ministers scrap the £20-a-week uplift as planned.
The Government plans to start phasing out the UC increase from the end of September, based on individual claimants’ payment dates.
The move would be the biggest overnight cut to social security since the Second World War and come as a huge blow for millions of families both in and out of work.
A YouGov survey for the Trussell Trust found that 11% surveyed, representing 670,000 people, said it was very likely they won’t be able to afford to switch on their oven to cook food after the cut.

And 900,000 people said they were very likely not to have enough money to travel to work or make essential trips such as medical appointments.
Care worker Christine from Berkshire will not be able to afford to get to work without the £20 a week.
"There’s no public transport alternative that would get me there on time – so I’ll be completely trapped.
"It's hard enough to survive as it is, and I only eat one meal a day at the moment because all my money goes on bills.”
Nat, a disabled person from Croydon, believes the cuts are "penalising (people) for being alive".
“Losing £20 a week means working out where to make cuts and that will probably be my food budget.," they said.
"I don’t have family nearby so I’m going to have to rely on friends.
"Removing the £20 isn’t an incentive for people to get back to work, especially those of us who medically can’t."

Shadow Secretary of State for Work and Pensions, Jonathan Reynolds said: “Over a million people forced to skip meals due to Government cuts is frankly disgraceful and unacceptable.
"Cutting Universal Credit will be a hammer blow to working families who are now facing tax hikes under the Conservatives, and will dampen our economic recovery.
"Time is running out for the Government to see sense, back struggling families and cancel their cut to Universal Credit.
" Labour would maintain the uplift and replace Universal Credit with a fairer social security system.”
Rishi Sunak has claimed people will not be forced into poverty when the Government cuts Universal Credit (UC) within weeks.
The Chancellor told the Commons: "I don’t accept that people will be forced into poverty, because we know, and all the evidence and history tells us, the best way to take people out of poverty is to find them high-quality work.
“We are creating jobs at a rapid rate – eight months of continuous growth in employment supported by this Government, traineeships, sector-based work academies, apprenticeships, Kickstart, you name it, we are delivering it to help those people in Liverpool get the skills and the jobs they need to help support their families.”