Currently, state help with the cost of home or residential help is available for those with assets below £23,250.
Labour says the pledge, costing an estimated £6bn a year, will double the number of those not having to pay.
It would bring England into line with Scotland, where personal care is free for those with the most severe needs.
In his keynote speech to the Labour conference on Monday, shadow chancellor John McDonnell said the move would be funded out of general taxation.
A future Labour government would pass legislation to enshrine a right to free personal care for those most in need, consulting on “eligibility criteria to ensure this system works for all”.
Labour said it would give more details of how it would be paid for in its election manifesto but the Conservatives said the opposition’s already extensive spending commitments meant “there simply won’t be enough money to pay for it”.
In anticipation of a general election this autumn, Labour has already pledged this week to axe prescription charges in England and remove the charitable status of private schools as a first step to “integrating” them into the state sector.
But the leadership remains under pressure over Brexit, with delegates set to vote on a motion pushing for a clearer Remain stance in a future EU referendum if Labour wins power.
Prime Minister Boris Johnson has promised to solve the crisis in social care, which has bedevilled previous Tory and Labour governments due to its cost and complexity.
Mr McDonnell said cuts to care funding since 2010 had left a million people not getting the care they need and “87 people dying a day waiting for care”.
Subsidising the cost of basic tasks such as getting in and out of bed and going to the toilet will enable more people to continue to live independently in their homes, he said.
Free personal care is something campaigners have long been calling for in England.
Scotland has already introduced it and Wales and Northern Ireland each provide some level of universal entitlement. In Wales the cost of home care is capped, while in Northern Ireland the over-75s get it for free.
Both the Tories and Labour have been talking about reforming the system for over two decades – Tony Blair came to power in 1997 promising to look at it.
But neither has managed it. Why? The cost and complexity have proved to be insurmountable barriers.
What is more, how much impact the policy has depends on the threshold that is set for accessing it. Even in Scotland, Wales and Northern Ireland the bar for getting help is set very high. Only those with the most severe needs get it.
The devil, as always, will be in the detail.
Based on Scottish figures, Labour said the move could save those currently self-funding their care almost £10,000 a year while 70,000 fewer families would be liable for “catastrophic” lifetime care costs in excess of £100,000.
Removing the distinction between health and care needs, Mr McDonnell argued, will most help families of dementia sufferers, who face the highest costs and, in many cases, have been forced sell their homes to pay for care.
“I believe the right to dignity in retirement is a part of that right to health at any stage of life,” he said. “The truth is our social care sector is a national scandal.
“The next Labour government will introduce personal care free at the point of use in England
“Funded not through the Conservatives’ gimmicky insurance schemes But, like the NHS and our other essentials, through general taxation.”
The pledge goes beyond what Labour promised in its 2017 election manifesto – in which it vowed to raise the minimum asset threshold for free care, cap the amount anyone has to pay during their lifetime and support free end of life care.
Under the current means-tested system, if an individual has assets worth more than £23,250, including property, they must pay the full cost of residential care without help from the council.
Those with assets above £14,250 have to contribute, but may get some help from state.
Labour, whose long-term aim is to provide free personal care to all working age adults, says support for over-65s will alleviate the pressure on the NHS by reducing delayed transfers of care from hospital and admissions to care homes and hospitals.
Mr McDonnell also pledged to close the gap in social care funding – Labour has already pledged to spend an extra £8bn a year over five years – and give local authorities extra support to provide care so services are not outsourced to private firms.
The King’s Fund think tank has estimated that free personal care could cost £6bn a year in 2020-21, rising to £8bn by 2030.
The organisation said Labour’s announcement was a welcome step but “it is not the same thing as free social care, and some people would still be left facing catastrophic costs.”
In its Spending Round earlier this month, the government announced a further £1.5bn in extra funding for social care and promised to look at giving councils more leeway to raise extra funds via council tax bills.