Another one bites the dust. The fourth biggest provider of home care for the frail, the Mears Group, with 30 branches in the UK, is abandoning its domiciliary care services. “We’re not the first and certainly won’t be the last,” says Alan Long, the executive director. Social care is collapsing because too few people are willing to work gruelling hours in disgraceful conditions for pitiful pay.

The new points-based immigration system announced by the home secretary, Priti Patel, on Wednesday will see many more companies fleeing the sector for lack of staff. With 122,000 vacancies, this decade’s 25% increase in people over 65 means another 580,000 staff will be needed to care for them over the next 15 years. In London, 40% of care staff are from overseas. Median average pay as of last March is a meagre £8.10 an hour, with parts of their hours unpaid: a quarter of staff are on zero-hours contracts.

Care workers' first complaint is never for themselves, always it’s their distress at not having time to care enough

Mears only takes public sector contracts from local authorities: it has no private clients. Whoever buys its care business, if anyone, will have to attract private families and milk them to cover the loss-making state-paid customers. “We can’t do that, we have no expertise in marketing to the private sector,” says Long. What councils pay companies varies widely, between £11 and £22 an hour, mostly the lower end. Staff are not paid travelling time: “Rushing from job to job, paid by the minute. Councils still commission 15-minute visits, against Nice guidelines. Staff stop in car parks to write up notes, unpaid for that.” Long says they need 25% more just to cover travel time.

Half of those who used to get care in 2010 no longer qualify, so staff only deal with “the gravest cases”, says Long, who deserve far longer visits. He’s not surprised they have a 40% staff turnover: similar work in the NHS pays more. Working in supermarkets pays more, without the emotional stress. “My son is an A&E doctor and he sees where these old people end up. That needn’t happen if they were cared for at home by people paid a salary for a fixed eight-hour shift, dedicated and permanent.”

Here’s the shocking circularity in the government’s position: caring will not qualify as sufficiently skilled to earn a visa, but all that brands this delicate work as “unskilled” is the appalling low pay. Rates for the job are only so low because the government, through local authorities, refuses to pay a fair or even a market rate for the job. The result is market failure, as the care sector collapses. In truth, however, it isn’t a market at all. Care services were outsourced by Margaret Thatcher in the 1980s to cut costs by allowing private companies to pay below public sector rates. But in the end, it was still the state paying for most of it: underpay, and people refuse to take the jobs.

I worked in a care home a few years ago, and it was by far the most skilled and difficult job I did in researching my book, Hard Work. Try looking after six frail, incontinent old people, feeding, washing, hoisting them in and out of baths, and above all talking to them as you are their only company. Six patients is lucky: staff vacancies often meant eight people to care for, backbreaking and heartbreaking. The care workers I worked with were run off their feet all day, and yet eager to be kind and patient. When I talk to staff now about working conditions, their first complaint is never for themselves, always it’s their distress at not having time to care enough. What counts as a “skill” if not empathy?

The quality of care is crumbling: last month I wrote about Garside House care home, recently rated “inadequate”, plunged into special measures and under police investigation, right on Westminster’s doorstep. Homes are closing every week, 101 shut in 2018. This week Derby City Council sold off three care homes, unable to raise the money for necessary improvements.

No 10 claims to be beavering away on Boris Johnson’s promise to “fix social care once and for all”. But how? The NHS is neat, with one employer, but social care has 18,500 separate employers and companies, as well as the 75,000 disabled people paying independently for personal assistants. Will there be a national rate and quality standard for every council and every company? As for funding it, Anita Charlesworth, the research and economics director of the Health Foundation, says it would cost £10bn to return social care just to the 2010 level of care. That should be a top priority.

But Johnson’s even more expensive care promise was to stop anyone needing to sell their home to pay for care – too afraid of the accusations of a death tax that plagued Theresa May’s plans from the 2017 Conservative manifesto which suggested that people may need to fund care by selling their homes after they’ve died. A mooted cap of £25,000 as the maximum anyone need pay, with the state picking up the bill thereafter, would cost another £4bn. That wouldn’t add a penny more for care, but just protect home-owning families’ inheritances.

The budget on 11 March will reveal Johnson’s true political priorities. Where, if anywhere, does social care come in his pecking order? And which comes first – restoring the quality and quantity of care for all, or ensuring homeowners’ families keep their inheritances? The auguries are not good, because one thing we know already: he has put the politics of immigration before the urgent need to employ more care workers for millions of the frail. If there is to be no more cheap foreign labour, he will need to raise pay steeply to attract enough British staff.

• Polly Toynbee is a Guardian columnist