A Housing Authority committee on Friday agreed to provide longer default guarantee periods for second-hand Home Ownership Scheme (HOS) flats and public flats bought by tenants.

From March next year, the period will be extended to 50 years, from the current 30 and 25 years.

The change, proposed in the Policy Address last month, is meant to facilitate the turnover of subsidised flats in the secondary market.

The chairwoman of the authority's subsidised housing committee, Cleresa Wong, said before the change, many interested buyers had a tough time with their mortgages because of the age of the flats.

"Let's say if a particular HOS flat is already 15 years old, that means the buyer would have only a guaranteed remaining period of 15 years provided by the authority to the banks he's going to borrow money from," she told RTHK.

"This is perceived to be one of the reasons why there aren't so many successful acquisitions of subsidised sale flats in the secondary market."