More surveyors reported a drop rather than a rise in new houses being put up for sale last month than in any other poll since June 2016, according to the Royal Institution of Chartered Surveyors (Rics).
Waning appetite from new buyers and uncertainty over Brexit has driven a slowdown in new instructions, which also fell to a 16-month low in London during April.
Buyer enquiries and sales remained negative in the capital, with nine per cent more respondents forecasting a further fall, rather than rise, in deals over the next three months.
Some 66 per cent more respondents reported a fall rather than a rise in London house prices during April, remaining unchanged from the previous month.
According to Rics, people putting their houses on the market are also becoming "increasingly realistic" over their asking prices, suggesting that homeowners have been lowering expectations about the sums which buyers are willing to pay for their property.
"Although there are signs of greater realism on pricing from vendors, there is little conviction in the feedback from respondents to the survey that activity in the housing market will pick-up anytime soon," said Simon Rubinsohn, Rics chief economist
He added: "Significantly, the key Rics buyer enquiries indicator remains subdued and sales expectations looking a year out are only modestly positive."
Analysis from LonRes earlier this week also found that new instructions dropped by 27 per cent across three of London’s prime areas, with the group noting that "it was sellers rather than buyers who were more cautious about the impact of Brexit".
Prices across prime central London were down 9.7 per cent in the first three months of 2019 compared with the same quarter last year.
Marcus Dixon, head of research at LonRes, said: "In quarter one pf 2019 Brexit dominated, with little indication of how the UK would leave the EU on the 29 March. Many prospective buyers chose not to transact. Fewer new homes reached the market and transaction levels fell back. Those who did choose to buy were aware of their position and negotiated accordingly, meaning bigger discounts and falls in achieved prices."
Dixon continued: "Looking ahead the prospect of months of negotiations over Brexit appears to be convincing prospective buyers that now, while we have some Brexit breathing space, might be a good time to re-enter the market. Agents are reporting a rise in applicants which could mean the next quarter is busier than the last."