Private companies buying up care homes for older people in England could undermine the government's ambition to create a universal care service, the regulator says.
The Care Quality Commission's annual report, external highlights how an increasing share of the care home market is owned by large firms - the five biggest have increased their share of the market by 26% in the last two years, driven by interest from US property investors. Between them they own around one in seven homes.
While there could be benefits, there are concerns the trend can lead to higher prices and a reduction in the quality of care - something the CQC says needs to be monitored.
Meanwhile, home care, providing support to help people wash and dress in their own home, has become more fragmented, with a greater number of smaller providers.
The CQC says this could create inefficiencies - nearly a third of these services are providing care to four or fewer people.
In contrast, there are few smaller care homes judged important for providing specialist and personalised care.
Small care homes have always represented a tiny proportion of the care home market, but over the last 14 years the numbers have fallen significantly, particularly those that combine care with nursing support, which are down by a quarter.
The CQC says the funding system remains fragile – people using care services either self-fund or, for the poorest, the state helps to pay for their costs.
And in some areas, providers are increasingly turning to self-funders, making it more difficult for councils to buy the care they need for those relying on state help.
CQC chief inspector of adult social care, Chris Badger, said the reshaping of the market was happening "largely by accident rather than design", driven by a combination of economic pressure and the problems some councils were having in buying services for those relying on state-funded care.
He said this government's renewed focus on social care – Andy Burnham made it one of his key priorities when he became prime minister – was welcome.
But he said it was important the market was "shaped around what's best for people".
"A clearer vision is needed," he added.
Hugh Alderwick, of the Health Foundation think-tank, said the report by the CQC "lays bare the massive challenges" facing the government.
"The prime minister's commitment to reforming the sector provides an opportunity to fundamentally redraw the state's offer on social care.
"But change is needed now to strengthen the fundamentals of the system.
"Councils need enough funding, the right skills and strong leadership to shape services around people's needs."
Prof Martin Green, of Care England, which represents care providers, said: "If the government and regulators are concerned by consolidation in the care sector, they need to take some clear and tangible action to support smaller care home providers."
He said changes to employer national insurance contributions, inflation and the rising cost of energy was making smaller homes unviable.
"Unless we get some real progress in a funding settlement, the trend of smaller homes closing will be a trend that will continue."
The Department of Health and Social Care said the report demonstrated the "scale of the challenge this government inherited", but said it was committed to overhauling social care.