The typical person entering residential care will face total bills of between £50,000 and £93,000, depending on where they live, according to analysis by Royal London.
Variations in house prices around the UK mean this could amount to anything from 18% to 56% of the value of the average house.
Royal London director of policy Steve Webb said: "Successive governments have failed to grasp the nettle when it comes to care costs. For over 20 years we have had a series of Royal Commissions, expert reports and policy papers, but little has changed."
In the recent Budget, Chancellor Phillip Hammond announced a new Green Paper on social care would be published later on this year and pledged there would be no ‘death tax' i.e. no posthumous levies on people's estates to pay for care during their lifetime.
The £72,000 cap on care fees is also meant to be coming into effect from 2020, as announced during 2015.
Even an average stay in a care home can "eat up half the value of your home, depending where you live in the country", according to Debbie Kennedy, head of protection at Royal London.
For residents in the North East of England, where the average house price is just under £129,000, an average stay of thirty months in a residential home costing £554 per week would "eat up" 56% of the value of their home.
For those living in London where the average house price is around £484,000, 30 months of average residential care costs of £666 per week would only account for around 18% of the value of that property.
For most people in later life, their family home is likely to be by far the largest asset on which they will need to draw to meet care costs.
The length of time for which someone stays in a residential home can vary widely, and for those with the longest stays, the total bill can exceed the value of the typical house in several parts of the UK.
Based on academic evidence that shows 10% of residential home residents have a stay of 6.5 years or more, for residents of Wales, Northern Ireland and four English regions (North West, North East, Yorkshire and East Midlands) such long-stayers could face a total bill in excess of the value of the average home.
Full results for Scotland, Wales, Northern Ireland and each English region for average stays in residential care homes are provided in the following table:
Kennedy added: "The whole system is a lottery and we need to find better ways of supporting people to cope with these large and unpredictable bills".
Webb concluded: "With an ageing population, more and more of us will have loved ones needing long-term care, and we could see a large part of the value of our family home taken up in care costs. The government's plans for yet another discussion document on social care later this year are far too slow. We need urgent action to address this funding challenge".
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