UK house prices fell 0.8% last month, according to the latest survey by mortgage lender Halifax.
The figure follows a 2.2% month-on-month leap in March, with experts pointing to the hike in stamp duty on buy-to-let properties cooling the market.
Howard Archer, IHS Global Insight's chief European and UK economist, said: "April's dip in house prices reported by the Halifax was likely largely the consequence of some of the wind being taken out of the housing market by stuttering UK economic activity and confidence, as well as a marked waning of interest from the buy-to-let and second home sectors following the rush to beat April's stamp duty increase."
Prices in the three months to April rose 9.2% compared with the same period last year, slowing from growth of 10.1% in the three months to March.
Both the quarterly and annual growth rates are at their lowest since last autumn.
Martin Ellis, Halifax housing economist, said: "Current market conditions remain very tight as the severe imbalance between supply and demand persists. This situation, combined with low interest rates and rising employment and real earnings, should continue to push house prices up over the coming months.
"Weakening sentiment regarding house price prospects and a dip in consumer confidence, however, suggest that annual house price growth may ease."
Experts also believe that the EU referendum could have an adverse impact on the housing market, pushing prices down further.
Mark Posniak, managing director at Dragonfly Property Finance, said: "As we approach the EU referendum, caution will almost certainly prevail and prices are likely to edge down further. People are starting to understand the magnitude of the Brexit vote and that will lead many to batten down the hatches.
"How the property market reacts to the result of the EU referendum vote is frankly anyone's guess. In the next month or two, the UK property market is entering the unknown."