The Tories temporarily increased the nil-rate threshold from £125,000 to £250,000, and from £300,000 to £450,000 for first-time buyers. However, this is due to expire in March.
Last week, property guru Kirsty Allsopp warned that scrapping the relief would spark “chaos” in the housing market.
Purplebricks managing director Jo Pocklington said: “Ending the stamp duty relief could discourage people from downsizing, which means there would be fewer properties available to buy – and this usually increases house prices.
“This could in turn discourage people from upsizing, which would mean a lack of properties becoming available for first-time buyers to get on the property ladder. The property market needs first-time buyers to keep it flowing smoothly.”
Research by Barclays found that about 85pc of owner-occupied homes in the UK have at least one spare bedroom, making them “under-occupied”. The bank urged Labour to consider offering households grants or the ability to offset moving costs against stamp duty to encourage people to downsize.
Paul Dales, of Capital Economics, said it would “make sense” for the Government to include a stamp duty carve-out for downsizers, “or relief for people for whom this is their final move from a big family home to a small home.”
He added: “It would be an inducement to free up living space not fully utilised.”