Average house prices dipped by 0.4% between April and May, according to the latest figures from estate agents Your Move and Reeds Rains.
The monthly fall was the steepest recorded by the firms since November 2011, and is thought to be as a result of the market 'holding its breath' before next week's EU referendum.
House prices in the capital dipped by 0.3%, equivalent to £1,769 month-on-month.
Annually, the agents report the prices were 6.8% higher in May when compared to the previous year. Excluding London, the East and the South East, values increased by 5.4%.
Your Move and Reeds Rains calculated the average house price in May as £293,599.
The index recorded the lowest number of sales for five years last month, as the fallout from the introduction of a stamp duty surcharge in April continued to have an impact.
One area which bucked the trend of monthly dips and steady annual growth was Slough, where house prices were 23% higher last month when compared with the previous year.
The agents say that the prospect of Crossrail and a rise in the number of tech jobs have had a positive effect on the area's property market.
“The housing market is holding its breath ahead of the EU referendum and after a rapid sprint at the start of the year," says Adrian Gill, director of Your Move and Reeds Rains.
"May’s correction in property values follows on from a surge in activity earlier in the year, when second-home buyers and landlords brought forward their purchases to avoid the surcharge," he says.
“With so much uncertainty in the UK economy, home sales have been subdued. While the total number of property sales did increase from the previous month, this month has seen the fewest May property sales since 2011, when the UK was still recovering from the recession," adds Gill.