More than eight out of 10 care home beds are provided by profit-driven companies, including more than 50,000 by large operators owned by private equity firms, research reveals.

Private companies now own and run 84% of beds in care homes in England used by older people, as local councils have almost totally withdrawn from a key area of social care they used to dominate.

The disclosure of the private sector’s huge market share has raised concerns because some of the biggest operators have large debts, are alleged to use tax avoidance schemes and drive down staff pay. The Care Quality Commission (CQC) watchdog has said inadequate staffing levels at care homes can lead to elderly residents receiving poor-quality care.

For-profit companies own 381,524 (83.6%) of England’s 456,545 care home beds, research by the IPPR thinktank (in partnership with Future Care Capital) has found, based on analysis of data from the CQC and Companies House, an increase on the 82% in 2015.

“The state has abdicated its responsibility for providing care over recent decades. The private sector may have filled this gap but it consistently puts profits before people,” said Harry Quilter-Pinner, a senior research fellow at the IPPR and co-author of the report.

“The fact that private equity-backed firms have taken over a significant share of the UK’s care provision, fuelled by debt and driven by the prospect of rising property prices and ever-lower care costs, puts our vital social care system at ever-increasing risk,” said Grace Blakeley, co-author of the report and IPPR research fellow.

In contrast, 13% of beds are provided by the voluntary sector and 3% by local councils, which for decades were the main provider of residential care for vulnerable older people.

“It’s shocking that so much of our social care is provided by large private providers who put profits before people and where too often the quality of care provided just isn’t good enough,” said Barbara Keeley, the shadow cabinet minister for mental health and social care.

“Social care is in urgent need of reform and yet the Tory government has abandoned responsibility for the care needs of older people and working-age people and they have no credible plan to fix this crisis.”

Ninety-one percent of councils have increased their use of private-sector care home beds since 2015 as alternatives have shrunk, the research shows. The IPPR analysed trends in bed use by 147 of England’s 151 councils. Overall, 133 of the 147 authorities had done that; just 14 had reduced their reliance on privately provided places.

Kensington and Chelsea council in London saw the biggest increase in private use in that time, rising by 50.9%. The next largest increases were seen in Westminster (42.7%), Bracknell Forest in Berkshire (32.6%) and Tower Hamlets in east London (25.5%).

Private firms have increased their domination of care home places over the past few years while the government has repeatedly cut core funding to councils for social care. While Whitehall spending has grown in recent years, the £21.3bn it gave to councils last year was £700m less than the £22bn it put into social care in 2010-11.

Boris Johnson has pledged to end what many critics claim is the “scandal” of social care. Fewer older people receive help with basic tasks such as washing and dressing than in 2010 as a result of government cuts.

The IPPR urged ministers to re-establish the state as a major provider of care homes by spending £7.5bn in order to provide up to 75,000 extra beds by 2030, with care provided by councils or other not-for-profit organisations, to help cope with the sharp rise in the number of over-75s and over-85s expected in the next decade.

A spokesperson for the Department of Health and Social Care said: “We expect everyone to be able to access high-quality, safe and compassionate care. Already 84% of providers are rated good or outstanding by the Care Quality Commission.

“People who receive care and their families should be able to have confidence that their care provider has a sustainable future.

“We have given local authorities an additional £1.5bn for social care next year, on top of their existing grants, to continue to stabilise the sector. The prime minister has said that the government will set out plans to fix the social care system in due course.”

• This article was amended on 19 September 2019 to add that IPPR research was done in partnership with Future Care Capital.

• This article was amended on 22 September 2019 to remove an incorrect list of the largest providers.