The Royal Institution of Chartered Surveyors (Rics) says the slump in house sales is forcing many more people to become either landlords or tenants.
In July, Rics members saw new instructions from landlords rise at their fastest rate on record.
But potential tenants are outweighing would-be landlords, and helping to push up rents in many areas of the UK.
The international credit crunch and the subsequent drying up of finance for new mortgages has produced the sharpest housing market slump seen since World War II.
The number of house sales has already fallen by 50% in the past year and with mortgage approvals already down by 70% it looks likely that sales will fall even further in the coming months.
"Frustrated vendors have been placing their property in the market to let as they have been unable to agree sales due to a lack of demand in the housing market," said Rics.
"Many would-be buyers have been forced to rent as the route to mortgage finance has been blocked," it added.
More lettings
According to the Rics survey of residential lettings, 43% more of its members reported a rise in landlord instructions than saw a fall during the three months to July.
The knock-on effect has been that rents have continued to rise, even though house prices are falling.
The Rics findings contradict those of some other recent rental surveys.
These have suggested that in fact new properties coming onto the rental market have outnumbered the increase in potential tenants.
The property firm Knight Frank has predicted that rents in central London may fall by up to 5% this year because of an oversupply of "forced landlords".
Warning
Landlords are now more inclined to keep hold of their rental properties, the Rics survey found, with only 2.1% opting to sell when their tenants' leases expired, the lowest proportion on record.
