Buy-to-let property owners are becoming increasingly concerned about falling rents, just as many need to refinance to more expensive, less flexible mortgage deals.

Data from the Royal Institution of Chartered Surveyors this week showed that landlords were more pessimistic about rental prices now than at any point in the past 18 months. Property owners in London were the most gloomy, with just 9 per cent more landlords expecting rents to rise than fall over the next three months, compared with 28 per cent in January.