Campaigners have warned that older people could be in for a "rude shock" when the government announces a cap on long-term care costs on Monday.

There have been widespread reports that the health secretary, Jeremy Hunt, has settled on £75,000 as the amount people will be expected to pay for care before the state steps in.

Campaigners say £75,000 would be too high and would mean many people would still have to sell their homes to pay for care.

The Dilnot commission recommended a cap of between £35,000 and £50,000, although the chancellor, George Osborne, is thought to have dismissed the possibility of that range on cost grounds.

But Stephen Burke, director of United for All Ages, which has been calling for a lower cap, said: "When families realise what is being proposed, they will be in for a rude shock. The government is sneakily shifting the cost of care further and further onto older people and their families. The £75,000 cap is the dampest of damp squibs. It is a con of the worst sort.

"There are fairer and better alternatives. The government for example could have raised the capital threshold for paying for care to £200,000 or higher. The failure by this government to meet the care challenge means that the next government will have to sort this out to meet the care needs of our ageing population."

The Labour peer Lord Warner, who sat on the Dilnot commission, said: "Essentially, we thought that the fairest way of doing this, and it wasn't a precise science setting the cap, but we thought it was somewhere in that range, £35,000 to £50,000.

"At that level, give or take, you would actually mean on average no-one would have to dispose of more than about a third of the value of their housing assets."

The Department of Health said the reports on the cap were "speculation". In an interview with the Telegraph, Hunt said: "The debate has been focused a lot on the level of the cap, but just having a cap means that pension companies and insurance companies will be able to offer products.

"That means we become probably one of the first countries in the world where people save for their social care just as they save for their pension. In many cases, it will just be an addition to your pension policy."

A Department of Health spokeswoman said: "We are determined to solve this decades-old problem which leaves people selling their homes and spending their savings. We are clear that the Dilnot recommendations are the right way to cap the potentially huge costs of long-term care, giving people the certainty they need to plan for their long-term care needs. We will bring forward detailed proposals shortly."

The Alzheimer's Society said a £75,000 cap would only help "the few".

"Today's reports may mean an important step forward in making the system of charging for care fairer but the devil will be in the detail," it said in a statement.