Investing in buy-to-let property could soon become even harder as stricter lending rules could mean landlords will soon need at least a 40% deposit to qualify for a mortgage.

Tighter lending criteria set to be enforced as early as this autumn by the Bank of England (BoE) will lock large groups of savers out of Britain's rental market, and limit it to an elite club of wealthy investors only.

Under the new system borrowers are likely to have to find much larger lump sums of cash to use as a deposit on a property than at present, as around half of buy-to-let mortgages sold today only require a 25% deposit, according to figures from Mortgages for Business.

The BoE reportedly plans to force lenders to ‘toughen up’ over concerns they have relaxed standards to much for landlords in recent years.

However, based on new rental requirements recently introduced by Nationwide, an average London property on the market at £500,000 with tenants paying the average London rent of £1,540 a month would already require a landlord to put down a £255,407 (54%) deposit to qualify for a Nationwide mortgage. This is based on an interest only mortgage requiring a £244,593 deposit (48.9%), plus £30,000 for stamp duty.