The average buy-to-let investor could make a loss of £325 a year if the Bank of England lifted interest rates by 2.5% over the next four years, new research suggests.
While few expect interest rates to rise this year, landlords are vulnerable if rates do increase faster than expected.
Investment platform Property Partner warned that profits from rental income could be completely wiped out by 2020 due to rising rates and the phasing out of higher rate tax relief from April 2017.
It would make buy-to-let unprofitable in seven out of 10 towns and cities in Britain, according to Property Partner.
Landlords in the South West are said to be most at risk, with investors in Salisbury facing a potential £2,984 loss in 2020.
Barely one in five areas will make a net rental profit of more than £100 a month if interest rates rise hit 3%, it said.
The report comes as buy-to-let buyers rush to beat April's stamp duty surcharge on investment properties, driving mortgage approvals to fresh highs.
Dan Gandesha, chief executive of Property Partner, said: "The phased withdrawal of mortgage interest tax relief will be felt across the country, but add in a modest interest rate rise, and many investors will see their rental profits completely wiped out.
“When you factor in April’s stamp duty hike on new property purchases, it’s clear that direct investment in buy-to-let no longer adds up. Traditional landlords from Land’s End to John O’Groats need to face up to the stark reality.”
Gandesha added: "In a few years, the whole structure of the UK housing market will have changed."