London-focused estate agent Foxtons saw profits plunge 64% in the first six months of this year.
Another estate agent, Countrywide, also saw profits tumble, also saw profits tumble, by 98% in its case. The firm said it would not pay a dividend.
Foxton's head Nic Budden said demand had slowed due to "unprecedented economic and political uncertainty".
House price surveys this year have consistently pointed to a slowdown in both house price inflation and transactions, as political uncertainty combines with a squeeze in household incomes to hold back buyers.
The Royal Institution of Chartered Surveyors said the reluctance of sellers to make a move had left estate agents with the lowest stock of properties for nearly 40 years.
Countrywide, whose shares fell to a record low in the wake of the announcement, said house sales exchanges were down 20%, 24% in London.
Countrywide said the first six months of this year were also tough in comparison with last year, which saw high levels of housing transactions brought forward to beat an increase in stamp duty changes and ahead of the EU referendum.
Its profits were £447,000, down from £24.3m.
Both agents are making deep cost cuts.
Foxtons pre-tax profits fell to £3.8m, down from £10.5m for the same period last year. Revenues fell 15% to £58.5m.
Foxtons said in its statement that there had been further cooling of the market in the second quarter of 2017, with the unexpected general election a factor in slowing activity.
It added that London was more greatly affected than the rest of the country.
Foxtons has been warning since 2014 that rapid price growth and strong demand in London had started to cool.
However, it said that in the longer term, it expected London to remain an attractive property market for sales and lettings.
Two of the country's estate agent chains have posted slumping profits in the face of a slowing housing market.