Estate agency Countrywide has warned that profits will come in at the "lower end of market expectations" amid reduced activity following the EU referendum and changes to stamp duty.
The UK's biggest listed estate agency said transaction levels were running "significantly below" last year.
In a third-quarter trading statement, the Countrywide said: "A combination of changes in stamp duty and the EU referendum in June means transaction levels are currently running significantly below 2015.
"We now expect transaction volumes for 2016 to be 6 per cent down on 2015 and, while too early to say definitively, it is likely that the level of market transactions in 2017 will be lower than 2016."
Sales in the period fell from £197m to £189m, with London bearing the brunt of the slowdown as volumes fell 29 per cent year on year. Overall house exchanges fell 1 per cent.
Shares in Countrywide and other estate agents fell sharply on Wednesday after Chancellor Philip Hammond announced a ban on letting agents' fees to tenants.
Chief executive Alison Platt said: "In light of the Chancellor's announcement yesterday regarding letting agents' fees, we look forward to working with the Government through this consultation process."