House prices fell 1.7% in May from the previous month, the largest monthly fall for 11 years, according to the Nationwide.
Annual house price growth halved from 3.7% to 1.8%, as the coronavirus crisis hit market activity.
The latest HMRC data showed that residential property transactions fell 53% in April compared with 2019.
“The medium-term outlook for the housing market remains highly uncertain,” the Nationwide warned.
“We have already seen a sharp economic contraction as a result of the necessary measures adopted to suppress the spread of the virus,” said Robert Gardner, Nationwide’s chief economist.