Image copyright Science Photo Library

Conservative plans to change social care funding in England may be derailed by councils, an ex-minister has warned.

The party wants to include the value of someone's home when deciding how much they must pay towards care at home - but allow them to pay after they die.

The Conservatives say the changes ensure fairness across the generations.

But Sir Steve Webb, the ex-Lib Dem pensions minister, says there is already a "lottery" in the way councils use existing deferred payment schemes.

Currently, people living in residential care can ask their local authority to pay their bill and recover the money from the sale of their family home after they die.

The Conservatives' plan would extend this right to those receiving care in their own homes, who would have to pay until they were down to their last £100,000.

But Sir Steve, who is now policy director for pensions specialist Royal London, said Freedom of Information responses showed a wide variation in the number of deferred payment arrangements set up.

Some councils in England had not signed any agreements to let people defer their payments, while in other areas more than 100 agreements had been signed.

Media playback is unsupported on your device Media caption "Every morning I'd make you a cup of tea. Do you remember?"

Sir Steve said: "It is clear that there is already a lottery as to whether people facing significant care costs can exercise their legal right to defer their payments under the existing system.

"The government will need to investigate very quickly why the present system is not working properly, otherwise there is a danger of building a new system on very shaky foundations."

The councils who had entered into the most agreements were Southampton City Council with 331, followed by Essex County Council with 208 and Middlesbrough Council with 165.

In contrast, 10 authorities - Westminster, Tower Hamlets, Hackney, Kensington and Chelsea, Haringey, Lewisham, Lambeth, Ealing, Blackburn with Darwen, and Luton - said they had not issued any.

How would the Tory social care plans work?

Image copyright ForMed Films

Under the Conservative plans nobody with assets of less than £100,000 would have to pay for social care. Currently anyone with assets of over £23,250 is expected to pay the full cost of their residential care and the value of their home can be taken into account.

But that is not the case if you receive care in your own home. Under the Tory plans the value of your home may in future be factored in, although the money would not be taken from your estate until after your death.

This means some people fear they will not be able to pass their homes down to their children.

The BBC's assistant political editor Norman Smith said Conservative sources were dismissing the prospect of any rethink over the plans, insisting there would be "no rowing back".

He said he had been told that while there would be a consultation, this had always been planned and it would only examine "the finer detail" of the policy.

Former Conservative minister Lord Willetts said the plan was "one of the bravest, most serious and most important" features of the Conservative manifesto.

He told Westminster Hour on BBC Radio 4 the proposal meant social care for older people would be financed by pensioners with "substantial assets" instead of younger people "struggling to make ends meet".

But Labour leader Jeremy Corbyn has accused the Conservatives of "forcing those who need social care to pay for it with their homes," labelling the policy a "dementia tax".

Lord Wood, former adviser to Ed Miliband, said the problem with the Conservative plan was that "it's not a long term system solution because it abandons the principle of social insurance".

The Lib Dems, meanwhile, said nine out of 10 homes would be eligible to be sold under the new regime, citing Land Registry house sale figures.

Calling for a "national movement" against the policy, Lib Dem leader Tim Farron said it was a "callous blow for people who have dementia and other long-term conditions, like multiple sclerosis and motor neurone disease, and of course their families.

"It is not just a massive mistake but a cruel attack on vulnerable people the length and breadth of this country."

The Conservatives appear to be fighting back online, with a paid-for ad on Google which pop up when users of the search engine type in the words "dementia tax".

The ad reads "The so-called 'dementia tax' - Get the real facts - conservatives.com", together with a link to an explainer about the party's social care policies on its website.