Buy-to-let landlords face a "severe dent" in post-tax profits following Chancellor George Osborne's tax crackdown.
Individual landlords will face extra tax bills of £2,000 a year and some will have to pay even more.
In his July Budget, the Chancellor announced that new restrictions on higher-rate mortgage tax relief for buy-to-let will be phased in over four years from April 2017.
Nimesh Shah, partner at London Chartered Accountants Blick Rothenberg LLP, said this will be a major blow for individual buy-to-let investors.
"Investors who rely on returns from their buy-to-let properties to top-up their income or use as a pension for retirement will now see their after-tax profits reduced.
“With interest rates expected to rise sometime in the next year, buy-to-let landlords with significant debt will see a reduction in tax relief, which will naturally result in higher costs and lower after tax profits."
Shah calculates that a 45% taxpayer with debt of £250,000 and interest charged at 3.25% will see their annual income tax liability increase by approximately £2,000.
Shah said serial buy-to-let landlords will probably look to operate their property businesses through companies, as the same restrictions do not apply.
He added: “The main rate of corporation tax is reducing to 18% by 2020, further increasing the difference between corporate and personal tax rates, making companies more attractive.
“However, for those with one or two properties, the associated cost and administration involved with operating a company is unlikely to make it worthwhile.”