The RICS price balance dropped to -8, having been flat in February and March.
The trade body pointed out that while this figure only signals a slight decline, it is nonetheless the most negative figure seen since November 2012.
The London market had a particularly tough month, with 65% more respondents saying prices fell over the month rather than increased, the weakest reading since February 2009.
However, prospects for price rises appear to be good.
Around 31% more respondents said they expected house prices to be higher in a year’s time, with the strongest sentiment in Scotland and the north west.
New buyer and sales remain flat
RICS reported that new buyer enquiries were more or less unchanged in April, following four straight months in which they had fallen significantly. It has now been 13 months since there was an increase in new buyers.
It was a similar story with sales which were mostly unchanged, having fallen back sharply in recent months.
New instructions fell, with a net balance of -7, though RICS noted this is the least negative reading seen since last September. Average stock levels on estate agents’ books now stand at 42.2.
Simon Rubinsohn, RICS chief economist, pointed out that the housing market generally sees an improvement in activity levels around this time of year, but noted that once this seasonal pattern is allowed for the underlying trends remain broadly flat.
Mark Readings, chief executive officer of House Network, suggested that uncertainty – largely because of Brexit – was slowing sales in the capital, but pointed out that it remains a good time for buyers with mortgage rates remaining low.
He added: “History tells us that as political uncertainty fades, we can expect a recovery, and sellers and buyers can now take advantage of a range of cost effective ways for marketing and buying property.”