Westpac, the country's biggest lender to landlords, is lowering the size of the deposits it will require from property investors, partially reversing last year's crackdown.

After a sharp slowdown in lending to property investors, Westpac and St George, which it owns, this month told mortgage brokers the maximum loan-to-valuation ratio (LVR) for new mortgages for property investors would rise to 90 per cent, up from 80 per cent.

The change means property investors need a deposit of 10 per cent of a property's value, compared with 20 per cent previously.

It comes as banks are offering more competitive interest rates to property investors in an attempt to boost growth now that this segment of the market is growing well below the Australian Prudential Regulation Authority's 10 per cent a year speed limit.