The cost of living crisis will prove "fatal" for some of the poorest families, MPs have been warned.
Food writer and campaigner Jack Monroe said millions of children were already living in poverty, with the situation becoming increasingly dire over 10 years of Tory rule.
Brits are being clobbered by rocketing energy bills, rising inflation and hikes to national insurance from April.
Monroe told the Commons Work and Pensions Committee: "There are millions of children living in poverty in Britain today and their home situations and their families' financial situations are already untenable and have been becoming increasingly untenable over the last decade.
"The impact of the cost of living crisis on those households is going to be, in some cases, fatal and that's not a term that I use lightly."
People are "eating less and skipping meals" as they are struggling to afford vital necessities, she said.
In testimony to MPs, Monroe warned that food insecurity was linked to high probability of chronic illness - creating a "catch-22" situation for disabled people who are at particular risk of struggling to get enough food.
She urged the Government to increase benefits by at least 6% from April, rather than the planned 3.1% rise.
The campaigner has been battling supermarkets to reduce the cost of the cheapest food ranges after highlighting the impact of inflation on everyday products.
She said: "That then makes it difficult to identify that a £20 a week food shop a few years ago gets probably about two thirds of what you'd be able to get for that £20 now.
"And that's not people deciding not to go to the theatre or not have legs of lamb or bottles of Champagne, that's people deciding 'we won't eat on Tuesday or Thursday this week' or 'we'll turn the heating off' or 'we'll skip meals'."
She said people should not be forced to decide on whether they can feed themselves adequately based on the price of a packet of pasta.
"It should be something that people don't have to do - those macro calculations walking round the supermarket. It should be something that's available to everyone regardless of their circumstances."
Food affordability has not improved - "it's that the expense of everything else has got worse", she said.
"Food is one of the most fundamental human necessities for survival. It's the last thing that any household chooses to cut in their budget.
"But rent has gone up, gas has gone up, electricity has gone up, council tax has gone up, the general cost of living has gone up to a point where people have less to spend on food in their household expenditure.
"In my experience of 10 years on the coalface of anti-poverty work, I can tell you that people are just eating less or skipping meals or having less nutritious food, bulking out on that 45p white rice and 29p pasta in lieu of being able to have fresh fruit and vegetables and nutritionally balanced meals."
Morgan Vine, head of policy and influencing at Independent Age, told MPs that older people were among the most vulnerable to rising energy costs.
“Older people are making choices every day between whether to put the heating on, or to boil the kettle or to skip a meal,” she said.
Millions of Brits will be hit by a major surge to their energy bills next month after regulator Ofgem confirmed the energy price cap will increase to a record £1,971 for a typical household.
The move would add £693 to the average annual energy bill overnight from April.
Chancellor Rishi Sunak has announced plans to take the sting out of the rise, which include a £150 council tax discount for people living in bands A to D and a £200 "rebate" off energy bills in October.
But the rebate will be clawed back from people’s bills in equal £40 instalments from 2023, when global wholesale gas prices are expected to fall.
It also comes as employees, employers and the self-employed will begin to pay 1.25p more in the pound for National Insurance from April for a year under manifesto-busting tax hikes imposed by the Government.
