Despite more than 900 buy-to-let mortgage deals being on the market at present, almost a quarter of landlords said a lack of suitable finance is preventing them from expanding.

Research by property site Property Let By Us found one-in-ten landlords had encountered difficulties when trying to take out a mortgage in the last 12 months.

Other aspects of the rental market are also becoming challenging. Almost 80% of landlords reported that tenants had fallen into arrears in the last year, many struggling with high rents and low wage growth.

Almost a quarter of landlords said they had served an eviction notice while 7% had to take tenants to court in order to evict them.

There was some good news for buy-to-let landlords, however, with void periods down 17% thanks to rising demand.

Jane Morris, managing director of Property Let By Us, said: “While the booming buy-to-let market looks like good news for landlords, the real picture is not so rosy. Spiralling rents are great news for yields, but the down side is that it brings with it a higher risk of rent arrears.

“Securing finance also looks like it is going to get tougher for landlords. A new high street crackdown now means landlords will need a bigger deposit and face tighter checks for a buy-to-let loan. High Street lenders are introducing strict criteria in a crackdown on the buy-to-let boom, which is feared to be pushing up house prices across the UK.

She added: “The amount landlords will be able to borrow is expected to fall by thousands and they are likely to face new tough lending criteria to secure a buy-to-let loan. Landlords must also prove that they are not wholly reliant on their rental income and that they will also be able to cope with void periods and any repairs to the property.

“Some lenders are introducing new affordability checks, which require landlords to answer such questions as how much they spend on household bills and childcare before they can get a loan. Lenders may also refuse loans to anyone dependent solely on a rental income and some providers expect applicants to have income of at least £25,000 a year from other sources.”