A Conservative government would consult on a possible cap on social care costs, Theresa May has announced.
The announcement comes as the Tories' opinion poll lead over Labour shrank amid public concern over manifesto proposals which were branded a "dementia tax" by General Election rivals.
It amounts to a significant concession after the Tory manifesto said proposals from the Dilnot Report on social care, which included a ceiling on the total amount any individual would have to pay, "mostly benefited a small number of wealthier people".
Speaking in Wrexham, Mrs May accused Labour leader Jeremy Corbyn of resorting to "fake claims, fear and scaremongering" over the impact of her plans.
She said: "This manifesto says that we will come forward with a consultation paper, a government green paper.
"And that consultation will include an absolute limit on the amount people have to pay for their care costs."
Speaking during a campaign visit to Hull, Mr Corbyn said a Tory U-turn on the "very dangerous and ill thought-out" social care policy would be "extremely welcome".
Mrs May came under intense pressure over social care following the launch last Thursday of the Conservative manifesto, which included plans to include the value of individuals' homes when calculating how much they must pay towards the cost of care in their own home, as is currently the case for residential care.
The manifesto guaranteed that no-one would see their total assets depleted below £100,000 as a result of care costs, and said that payments for home care could be deferred until after death in order to prevent people having to sell their properties during their lifetimes.
But the document appeared to reject the principle of a cap on contributions, which had been due for introduced at a level of £72,000 from 2020.
Now Mrs May has reopened the door to the implementation of a cap, which would save those with long-lasting and extreme conditions from losing hundreds of thousands of pounds from the value of their homes.
But she insisted: "We have not changed the principles of the policies we set out in our manifesto. Those policies remain exactly the same.
"There will be aspects of how this operates that we will consult on through the green paper. We were honest that we were going to have a green paper and would be consulting people on how the system operates.
"What we have done, which other parties have signally failed to do, is to recognise the challenge that we face, to respect the needs and concerns of the British people and to provide a long-term plan for sustainable social care which means that elderly people in this country won't have to worry about how their social care will be paid for in the future."
Mrs May's announcement was leaked by former cabinet colleague George Osborne - now editor of the Evening Standard - in a tweet half an hour before she spoke, in which he said: "U-turn coming on social care. There will be a cap."
Answering questions before Mrs May confirmed her plans, Mr Corbyn said: "A Tory U-turn on social care would be extremely welcome because I want this country to face up to its responsibilities to those who need care, like the frail and elderly, those with special needs,those with severe disabilities, those with learning difficulties.
"Our proposals are that we will refund social care, putting emergency money into it now so those million people waiting for social care don't wait.
"And we won't get involved in this horrible policy that is being put forward which will actually damage families and family income, damage people, break up relationships, all kinds of horrible things will happen from their very dangerous and ill-thought out social care policy."
He added: "And if George Osborne is at last doing something useful in his life such as supporting proper funding of social care, then thank you George for that and I urge you to read very carefully what's in our manifesto on social care."
Responding to the U-turn, Liberal Democrat former care minister Norman Lamb said: "This is Theresa May's manifesto meltdown.
"This is not strong and stable. It's panic and U-turn."
Scottish National Party leader Nicola Sturgeon tweeted: "PM not so strong and stable after all ... and can't be trusted to protect pensioners."
Ukip economic spokesman Patrick O'Flynn said the new policy was "wholly inadequate" and raised more questions than it answers.
Mr O'Flynn said a cap in six figures would be "wholly unacceptable" and urged pensioners to put pressure on the Prime Minister to commit herself to a specific and lower figure.
"The Conservatives are in full meltdown on this issue," said Mr O'Flynn.
"But just telling people they will consult on a cap on social care bills is not good enough.
"Older voters need to know and deserve to be told what that cap will be.
"At the moment the Tories could just announce after the election that it will be £250,000 or even £300,000."
At one stage Mrs May shook her head in disagreement as a reporter suggested she had performed a "U-turn" on her policy.
Under repeated questioning about social care, her voice cracked and she became visibly angry, repeating: "Nothing has changed, nothing has changed."
Asked about the so-called "dementia tax", she shook her head repeatedly, saying: "I'm sorry, you are using terms that have been used by the Labour Party to try and scare people in this country.
"This is a system that will ensure that people who are faced with the prospect of either requiring care in their own home or needing to go into a home for care are able to see that support provided for them and don't have to worry on that month-by-month basis where the funding is coming from."
Mrs May's climbdown came after a clutch of opinion polls showed Labour eating into her party's lead.
The latest, by Survation for ITV's Good Morning Britain, showed the Conservatives on 43%, down five points on the previous week and nine points ahead of Labour who were up five on 34%.
Over the weekend, ministers were adamant there would be no going back on the plans set out in the Conservative manifesto.
But Liberal Democrat leader Tim Farron vowed to mobilise a national campaign against what he called the "dementia tax" because of the potential impact on sufferers of the debilitating condition.
Lib Dems launched an online "scrap the dementia tax" petition at dementiatax.org.uk.
In a sign of how the issue had taken centre stage in the election battle, both Tories and Labour bought ads on Google which pop up when users of the search engine type in the words "dementia tax".
In a reflection of the party's concern at the tag being attached to its policy, the Conservative ad read "The so-called 'dementia tax' - Get the real facts", together with a link to a party website.
Labour's ad linked through to a page attacking Mrs May's manifesto, with "Tory threat to pensioners" at the top.
In an apparent sign of Mr Osborne twisting the knife on the woman who sacked him from the Cabinet, an Evening Standard editorial described her announcement as "an astonishing U-turn" and said: "It is not encouraging that the original proposals were so badly thought through."
Denouncing a "weekend of wobbles" leading to a "hasty" change in tack, the editorial said: "The Tory manifesto has only just come out, and already it is being rewritten. Now ministers will struggle to explain where the cap will be set, how much it will cost - and why the manifesto originally said that previous proposals for caps on care costs were unfair.
"Just as well, really, that this manifesto wasn't written on a tablet of stone."
Mr Farron said: "May's manifesto meltdown changes nothing. As Theresa May has made clear herself, nothing has changed and her heartless dementia tax remains in place.
"This is a cold and calculated attempt to pull the wool over people's eyes. Theresa May still wants to take older people's homes to fund social care.
"Families deserve to know exactly how much of their homes would be up for grabs now, not after the election."
Labour's election co-ordinator Andrew Gwynne said: "Theresa May has thrown her own election campaign into chaos and confusion. She is unable to stick to her own manifesto for more than four days. And by failing to put a figure for a cap on social care costs, she has only added to the uncertainty for millions of older people and their families.
"This is weak and unstable leadership. You can't trust the Tories - if this is how they handle their own manifesto, how will they cope with the Brexit negotiations?"
Speaking after the u-turn was announced, Mr Corbyn told reporters: "They haven't said what the cap is.
"They haven't explained to the millions of people who are desperately worried at the moment about what kind of care they are going to get in the future, desperately worried for children as well about how their parents are going to be looked after.
"This is a government in chaos and confusion."
He dismissed Mrs May's claims that he was "scaremongering" over the social care plans, after Labour went on the attack over the proposals.
Mr Corbyn said: "I'm not playing on anybody's fears, I'm expressing the fears that a lot of people have and I suggest the Prime Minister, instead of blaming me, should look to herself and look to her team and look to the policy, or lack of policy, that's she's put forward.
"This isn't strong and stable, this is chaos."
Sir Andrew Dilnot, who led a major review of social care for the Government in 2011 which suggested a cap, told BBC Radio 4's World At One: "Until we actually see what proposals come forward at the end of a green paper, we can't be sure, but only a few days ago the Government was saying a cap was not a good idea.
"I think they've now recognised it is a good idea and I think those who want to see a sensible system put in place simply need to keep the pressure up over the next few months so we do end up with a system that can work, instead of a system that misses one of the crucial elements of the problem."
Health Secretary Jeremy Hunt last week said the Tory manifesto was "completely explicit" that the idea of a cap had been dropped because it was not "fair".
"The reason we don't think it is fair is because you could have a situation where someone who owns a house worth £1 million or £2 million and has expensive care costs of perhaps one or two hundred thousand pounds ends up under that proposal not having to pay those case costs because they are capped," Mr Hunt told BBC Radio 4's Today programme on May 18.
"Those costs get borne by taxpayers - younger families, possibly themselves struggling to make ends meet. We don't think that is fair on different generations."