Last week, Nationwide Building Society announced new restrictive buy-to-let lending criteria that will require landlords to receive a much higher rental income to mortgage cost ratio moving forward.

From May 11, landlords will need a rental cover requirement of 145% compared to 125% and at least a 25% deposit.

As a result, low yielding rental properties could become unmortgageable, forcing some property investors to exit the market altogether. And it is expected that other lenders will soon follow suit.

The announcement comes after a series of other blows to landlords, including changes to wear and tear allowance, a 3% Stamp Duty surcharge and Section 24 of the Finance (No. 2) Act 2015 - which means that the cost of finance will no longer be an allowable expense for buy-to-let investors.

Steve Bolton, Founder and Chairman of Platinum Property Partners (PPP) is currently co-leading a legal challenge against the Government in a bid to abolish Section 24, which will force hundreds of thousands of landlords to either sell up or drastically increase rents.

And now, stricter lending criteria could reduce the critical supply of rental property even further.

Steve commented: "If the Government is concerned about buy-to-let investment overheating the housing market, then enforcing stricter lending criteria is a sensible measure. Taken in isolation, the pre-emptive move is responsible, as increasing the rental income to mortgage payment ratio will ensure investors don't overstretch themselves. No one wants a boom or bust housing market.

"But this is what should have been done first, and only confirms what we were all thinking initially - that all of the other measures that have been put in place, such as the Stamp Duty surcharge and Section 24, are in fact tax grabs.

"Making buy-to-let mortgages more difficult to qualify for will have the unintended consequence of further reducing the number of rental properties available and increasing costs for tenants.

"The Government's quest to get people onto the property ladder without any consideration for renters it outrageous. The amount people pay in rent directly impacts what they can save towards a deposit.

"It doesn't affect HMOs (Houses in Multiple Occupation) and affordable high quality accommodation that PPP provides. But there is still a high demand for single tenancy rental properties from low income families. If people stop investing in those types of properties because of low yields and higher deposit requirements, who will pick up the slack?"