The housing market is facing a buy-to-let "storm" as investors rush to buy property before the stamp duty surcharge comes into force in April.
The storm will then subside which may lead to a shortage of supply and force rents upwards.
New research from the Association of Residential Letting Agents (ARLA) showed a seasonal lull in the private rental market in December.
The number of prospective tenants dropped 15%, while the supply of properties also marginally fell, from 189 per branch in November to 182.
But managing director David Cox said this was the “calm before the storm” about to engulf the housing market.
“Buy-to-let landlords determined to complete purchases before the changes come into force in April are storming the UK housing market, meaning the lull we’d usually see is less significant."
One in four letting agents report an increase in buy-to-let investors but they anticipate an immediate decline after the surcharge is introduced, according to ARLA’s private rental sector report.
Cox added: “After April, we’re very likely to see the number of buy-to-let properties on the market begin to decrease, and this will most certainly have a detrimental effect on renters across the country.”
The number of tenants seeing rent hikes also dropped in December, with only 18% of letting agents reporting a growth in rent, down from 23% in November.
Cox added: “As we’d expect in December, the UK saw a lull in activity, with people putting off any moves until January.”
He forecast a drop in the number of rental properties on the market after April. "This will most certainly have a detrimental effect on renters across the country.”