THE Housing Board is tightening eligibility rules to decide who qualifies for heavily-subsidised public rental flats.

The revised rules come into immediate effect.

The move will differentiate those truly deserving cases from those who actually have alternative housing options, National Development Minister Mah Bow Tan told Parliament on Friday.

The HDB will now consider an applicant's income and assets.

Those who have previously taken a housing subsidy, and still have significant savings or savings from a previous flat sale, will no longer qualify.

In addition, applicants must not have owned a private property before, or have a child who owns private property, or have a spare room in his HDB flat.

These new rules will be implemented on top of existing rules, which will still apply.

This includes: being a Singapore citizen; at least 21 years of age; not have owned or sold an HDB flat or private property in the last 30 months; not had two housing subsidies; and does not have a monthly income of more than $1,500.

Mr Mah also said on Friday more help will be provided for low-income existing tenants of HDB's rental flats.

Such needy cases will get additional rent rebates under the GST offset package.

For tenants paying rents pegged at market rents, HDB will continue to peg it to 2005 levels, instead of more expensive, current levels.

It will also suspend the alignment of rents for 2009, which originally would have raised tenant's payments according to their income.

HDB will also build more rental flats to boost supply. Since 2007, about 930 rental flats were made available through conversion of old HDB flats.

This year, another 1,450 will come online through building more, or converting more old flats.

By 2012, HDB will boost supply from the current 42,000 level to 50,000.