Rents fell an average of 0.3% on the year in May to £901 a month, the first annual fall since 2009, figures from HomeLet show.
Rents fell more sharply in the capital, down 3% on the year in the Greater London area to £1,502.
Chief executive Martin Totty said the slowdown mirrored a similar picture for the rest of the housing market, with landlords facing a difficult balancing act between ensuring affordability for tenants and covering their own rising costs.
