More than two thirds of home owners aged over 65 have at least two spare bedrooms, but only 2 per cent expect to move in the next six months.
The findings come in new data released as part of the English Housing Survey today.
It shows that in 2017-18, 9 million households were living in under-occupied homes, which are defined as properties with at least two spare bedroom.
Home owners accounted for 7.9 million of these households, with over 54 per cent living in under-occupied homes.
Under-occupation is highest among older age groups, with 67 per cent of home owners aged 65 or over living in homes with at least two spare bedrooms.
This is equivalent to 3.6 million households, but only 2 per cent of people in this age group expect to move within the next six months.
For those older home owners who did express a desire to move, downsizing was the primary reason given.
Just Group communications director Stephen Lowe says: “It demonstrates that once people have bought a family home, they tend to stay put even many years after their children have flown the nest.
“There are many reasons for this – they like the neighbourhood, the extra space to entertain family or friends, the happy memories, and perhaps they see it as a continuing good investment.”
He adds: “Overall it does raise a bigger question about how easy or costly it is to downsize and whether there should be more incentives to move to free up space.
“While we are emotionally invested in our homes, we are also financially invested and for those who are happy staying put, but find their finances become more stretched through retirement it is likely equity release will become a bigger part of their financially planning.”
Private Finance mortgage consultant Chris Sykes says: “The cost of stamp duty is discouraging these empty nesters from downsizing, leaving them in homes too large for their future needs, but too costly to give up.
“As a result of this inactivity at the top end of the ladder, housing stock is limited and the UK property market is somewhat paralysed.
“To free up housing stock and re-energise the property market, we are calling on the UK government to introduce a stamp duty exemption for last-time buyers.
“Minimising the tax liabilities for older generations could encourage and enable them to finally downsize, freeing up housing stock and thereby helping to fix the supply issue that has hindered the market for so long.”