The D.C. City Council gave unanimous final approval last night to a controversial rent control law that allows landlords to receive higher rent increases on vacant apartments, exempts more properties from controls and establishes a $15 million rent-subsidy program.

Before a capacity audience of about 140 people, the council put the provisions of the new measure into effect immediately by passing identical emergency legislation just 2 hours and 13 minutes before the midnight expiration of a rent law that has been in place since 1981.

Mayor Marion Barry, who had waited at the District Building for the outcome of the vote, signed the emergency legislation almost immediately after the council meeting ended.

The permanent bill will be in effect for 6 1/2 years after it is signed by the mayor and undergoes a 30-day congressional review period.

Meanwhile, as a result of the emergency legislation, tenants will face increases of 12 percent rather than 10 percent on vacant apartments beginning today. In addition, landlords who win city approval of hardship petitions will be authorized to receive a 12 percent rate of return on their properties instead of 10 percent.

Under normal circumstances, however, routine annual rent increases for the estimated 120,000 units under rent control will still be tied to the metropolitan consumer price index and be limited to 10 percent.

The new legislation contains three forms of vacancy decontrol -- the lifting of rent controls on apartments as they become vacant.

All single-family rental property owned by individuals will be exempt from controls as they become vacant and, on a case by case basis, buildings 80 percent vacant will be exempt from controls beginning today.

In four years, all rental units will be exempted from rent controls if the city's vacancy rate is at least 6 percent and a rent subsidy program is funded and operating. The city's current vacancy rate is 2.4 percent, according to a recent report by the U.S. Department of Housing and Urban Development.

The council approved the new rent control measure despite intense pressure from tenant groups and the labor community to get the council to adopt a bill that would have continued the old law unchanged. That bill was introduced by City Council Chairman David A. Clarke and supported by five other council members.

The council had been sharply divided over the rent issue, and a seven-member majority succeeded in initially approving the new measure on April 16.

Last night's bill contained some minor amendments, including one that would exempt only single-family houses owned by individuals rather than corporations.

Last night, council member Frank Smith (D-Ward 1) tried repeatedly to delete vacancy decontrol provisions from the bill but was defeated each time by the seven-member majority. In the end, Smith and other members who had supported the Clarke bill voted for the amended bill, saying that the city had to have a rent control law.

After the meeting, City Council member John Ray (D-At Large), a chief organizer of the seven-member voting bloc, said that the new law "is far superior to the law we had on the books" and would help to place vacant property back on the market through special incentives offered to property owners.

Tenant representatives, however, said that they will seek to nullify the new law through a voter initiative.

Tenant activists have viewed the legislation as a major step toward phasing out rent control because of the vacancy decontrol provisions.

Tenants have also argued that rent control protections make decent and affordable housing available for all residents and that higher rents would force some residents out of the city.

Landlords blamed rent control for a deterioration of the quality and quantity of rental housing in the District and tried to convince the council that higher rents in some cases were needed to maintain buildings properly.

Supporters of the Clarke bill turned out in such large numbers last night that more than 100 were forced to wait outside the building and in hallways near the council chamber. Scores more found seats inside, however, and as the final vote was taken, many began chanting: "Shame, shame, shame. The seven are to blame."

As the chanting became louder Clarke told the audience that if they could not respect the council they should respect him as chairman. The chanting stopped immediately.