The figures came from quarterly research of almost 3,000 landlords conducted by the Residential Landlords Association (RLA).
It prompted the RLA to warn of a perfect storm hitting tenants in the rental sector with the number of properties available set to fall while increasing demand drives rent increases.
Its Welfare Reform and Universal Credit: The Impact on the Private Rented Sector report found that in the last three months, 33% of landlords had experienced an increase in tenant demand, driving future rent increases.
Over the last year the RLA research found that 43% of landlords had increased rents and that 47% planned to increase them in the year ahead.
The organisation said the government needed to reappraise the way landlords were taxed to encourage more to increase the size of their portfolios and increase the availability of properties for tenants.
RLA chairman Alan Ward said: “As demand continues to increase for homes to rent, punitive tax changes are discouraging investment by the majority of good landlords who want to provide accommodation.
“While efforts by the government to support institutional investment in the sector are welcome, this will remain a drop in the ocean.”
He added: “To meet demand, we need pro-growth taxation that actively supports and encourages the majority of landlords who are individuals providing good housing, to invest in the new homes to rent we so desperately need.”