House prices fell by 0.9 per cent this month, equivalent to £2,647, according the first data showing how property prices have been impacted by the Brexit vote.
Rightmove's report on the value of homes coming to market also found enquiries in the two weeks after the referendum were down by as much as 16 per cent compared to the same period last year.
The data was collected over the last four weeks - covering two weeks before the EU referendum and two weeks after.
The numbers follow a survey from experts who predicted house prices would fall after the referendum result. Some analysts have said prices could fall by five per cent over the second half of 2016.
Looking to sell? Here's some advice
Miles Shipside, Rightmove's director, said people looking to sell their homes need to be asking for the right price to move quickly.
He said: "If you're putting your property on the market and are keen to sell, then pitching your asking price too high would be counter-productive in the current environment.
"Buyer affordability is already stretched and they will be looking for extra reassurance that they're getting the best priced home to suit their needs.
"Pricing competitively will tempt buyers, some of whom are sitting on their hands."
Jeremy Duncombe, director of Legal & General Mortgage Club, said: "Given the uncertainty that has followed the UK's decision to leave the EU, it's not surprising that house prices have decreased month-on-month for the first time in a while.
"It's clear that demand for property still exceeds the housing supply on offer, just as it did before the referendum. The recent report from the House of Lords calling for 300,000 new homes to be built per year will provide some much needed pressure in this area."