Julia has a system to survive. Every month, she maxes out her overdraft: £1,000 in the red to pay for utility bills, council tax, mortgage, and food for herself and her daughter. Then the 49-year-old’s salary puts her back in the black – and she does it all over again.

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This is the definition of precarious living: a life where, in Julia’s words, “everyday needs pile up”. The overdraft isn’t enough to keep her head above water. In the past nine months, she’s fallen into £5,000 worth of credit card debt. As we talk, Julia writes it all out – listing basic family costs, item by item: replacing broken furniture (“It was falling apart,” she says); buying her daughter shoes and a uniform for secondary school, and a bike to get there; hiring a plumber to unblock the toilet.

She can’t remember the last time she went out with friends or bought something as a treat. “I have holes in my clothes,” she says.

You may be wondering what Julia does for a living. In a climate of underemployment, insecure jobs and cuts to social security, it would be easy to imagine she was struggling on a zero-hours contract, or perhaps a disability benefit. But Julia is a teacher. If you’re in Norfolk, she may be the one meeting your child at the school gates in the morning or taking your next parents’ evening. She earns what most of us would call a decent wage: £34,000 a year. To say she works full-time for that seems misleading. It’s closer to a 60-hour week, and she’s exhausted. She gets to the school at 7am, prepares for class, teaches until 4pm, and marks homework in the evening – and is rewarded with debt and stress.

Julia – not her real name – prides herself on being careful with money, and can’t stand the thought of being recognised by parents or colleagues as having a debt problem. To pay the bills, she tells me she’s thinking of taking on work as a private tutor at the weekends. A teacher with a second job on the side. “If people on my salary are struggling, God help the parents on £20k,” she says.

When John McDonnell announced at the Labour party conference on Monday that a Labour government would cap credit card charges, he highlighted the growing crisis facing families like Julia’s.

A Guardian series this month chronicled the scale of Britain’s debt timebomb: more than 8 million people living under the weight of £200bn of unsecured credit.

But on top of the levels of debt this country’s families are facing, it’s what’s driving them there that stands out. This isn’t a splurge on a new car or designer clothes – but payments for council tax or electricity bills.

The gulf between wages and living costs is such that credit cards, loans and rent-to-own deals are now a financial sticking plaster: a frantic attempt to patch up the gaps left by an income that barely covers a home, food and heat. Certain sections of society are particularly vulnerable: gig economy workers, young people, private renters and lone mums or dads. New research by the charity Gingerbread shows that a third of single parents are in debt, with – staggeringly – nearly a quarter of those in debt owing at least £10,000.

Credit cards, loans and rent-to-own deals are now a financial sticking plaster

Debt is the inevitable result of a system in which living costs rise as wages and benefits fall. What’s coming into the average family’s bank account nowadays hardly comes close to what needs to go out. Since 2008 another 4 million people have been pushed below the benchmark for what’s classed as an adequate income to afford decent living standards – as calculated by Loughborough University – due to increasing pressure on household budgets.

This has been creeping up for years and is only set to get worse. The pressure on households has just officially jumped, with the cost of basics such as clothing, shoes and fuel pushing core inflation up to its highest since 2011. The Joseph Rowntree Foundation has calculated that over the next five years the cost of living could rise by up to 10%.

“The cost of living” is in many ways a political euphemism for relentless pressure. The stress in the pit of your stomach of how to pay the bills coming in. Yet instead of overseeing policies to lift the burden, the government is adding to it: freezing working-age benefits, cutting tax credits, and offering token changes to the public sector pay freeze.

Next time a minister declares that employment alone is enough to solve people’s financial problems, I would suggest they talk to Julia. Vast chunks of the population now need loans simply to make ends meet. If this is not a national crisis, nothing is.

• Frances Ryan writes the Hardworking Britain column for the Guardian