Half of landlords (49%) have experienced rental arrears in the last six months and 37% are worried about the likelihood of arrears in the months to come.
The finding emerges in a poll by the National Landlords Association which interviewed 546 landlords.
The survey also shows a pronounced tendency towards longer tenancies, with 54% of tenancies now lasting between two and three years, 32% lasting over four years and 12% over five years.
The research also shows that the proportion of landlords who have added property to their portfolios rose to 12% in the second quarter of this year, with 22% expecting to make further purchases in the next 12 months.
This was despite nearly a third (31%) finding they were unable to expand because they could not raise the money.