The government on Thursday said it is confident that its plan to get rid of poor quality subdivided flats will not leave residents homeless and there'll be plenty of public housing available for them.

In his Policy Address on Wednesday, Chief Executive John Lee said a registration system will be introduced, and subdivided units will have to be at least eight square metres in size, with a window and separate toilet.

At a media briefing on Thursday, officials added that other requirements will include that rooms have a height of at least 2.3 metres, that the window opens into an area that isn't enclosed on all sides, and that the toilet has a ventilation system.

The units must also comply with fire safety regulations.

About 30 percent of the city's 110,000 subdivided units are expected to fall foul of the new rules.

A 12-18 month registration period is expected to begin in the fourth quarter of next year, with owners given a grace period of up to two years following registration to comply with the new rules.

Deputy Financial Secretary Michael Wong, who leads the Task Force on Tackling the Issue of Subdivided Units, said there's an abundant supply of public housing for residents of flats that don't make the grade.

“We've looked at the current composition of the residents of subdivided units. About 60 percent will be eligible for public housing. So the key is to provide an adequate quantity of public housing units, and that's something, I will say, where we are succeeding,” he said.

“For the coming five years, even if we do not count the number of light public housing, we're able to provide more than 30,000 public housing units every year.”

He said tenants affected could also move into transitional housing or subdivided flats that do meet the minimum standards.

Meanwhile, Permanent Secretary for Housing Rosanna Law said rewards of about HK$3,000 will be offered to people who provide tip-offs about public housing tenancy abuse.

The move will be part of the "Cherish Public Housing Resources Award Scheme" to be launched by the Housing Authority in January.

Law said people will only get a reward once a recovery notice for a flat is issued, saying the authorities are setting conditions to deter indiscriminate reporting.