In a rush of last-minute legislative action yesterday, the Prince George's County Council unanimously approved new laws that could triple the county's contracts with minority-owned firms and altered laws governing day-care facilities.

In its final legislative session for the year, the council also voted unanimously to elect William Amonett to succeed Floyd E. Wilson as council chairman, a choice that several council members said had been agreed to in July. The minority procurement law, which has been in the works for more than a year and is the fruit of recommendations offered by County Executive Parris N. Glendening's minority procurement task force, will increase from 10 percent to 30 percent the amount of county contracts signed with businesses owned by blacks, women, Asian-Americans, Hispanics and other groups defined as minorities under the law.

Sponsors of the bill admitted that the 30 percent goal probably could not be met in its first year because there are not now enough minority businesses to bid on projects. They said they did not expect that to be a problem after the first year.

Larnzell Martin, a lawyer who served on the task force, told the council yesterday that the new bill is an "effort to get the county out of its passive mode" in attracting minority contractors.

"Prince George's County must determine whether or not it's going to put forth an assertive, affirmative effort to attract minority contractors," Martin said.

The county's current minority procurement law does not outline a process for accomplishing its 10 percent goal. But last year, Central Services Director Ruth Webbon said, about 10 to 11 percent of the county's business went to minority entrepreneurs. The new law will provide a schedule of bonus points to be awarded to minority-owned firms during the bidding process. The law also awards additional points to minority-owned enterprises located within the county.

Council members Sue V. Mills and Anthony Cicoria questioned the bill's intent and the effect it might have on large, majority-owned businesses in the county.

But both later voted in favor of the bill even though Mills continued to say that she felt the 30 percent goal was set too high.

Martin and other members of the task force said that the figure was reached after conversation among its members, who represented various county businesses.

"It was a mutual agreement . . . that if we could get almost 11 percent by doing practically nothing, then . . . 30 percent would be a reasonable number," Webbon said.

Paul Rodbell, who as a spokesman for the Prince George's Chamber of Commerce played an instrumental role in the compromise version of the bill, said the measure was the best "to accommodate competing interests."

The bill as passed applies only to purchases made through the county's procurement office. This would include construction, supplies and professional services. Other government agencies, such as the school system, the libraries and bicounty agencies, including the Washington Suburban Sanitary Commission and the Maryland-National Capital Park and Planning Commission, have their own purchasing processes and are not affected by the bill.

Amonett officially will take over as the council's chairman at noon Tuesday. Amonett, who lives in Brandywine and represents part of the rural southern end of the county, has served as chairman twice before for one-year terms.

Although current Vice Chairman Jo Ann T. Bell had expressed an interest in the job, there were no other names put in nomination yesterday. Hilda Pemberton was unanimously elected to succeed Bell as vice chairman.

In action affecting day care, the council approved a bill prohibiting persons with criminal records of child abuse from operating or working at day-care centers and a second bill bringing county zoning regulations over at-home day care into accord with state laws.

The first measure, aimed at curbing the incidence of sexual and child abuse at day-care centers, requires that applicants for license or license renewal be screened by the county health department for criminal backgrounds.

"This is a problem of such magnitude and such gravity . . . it's going to take many layers of government to solve the problem, but we have to start somewhere," said Mills.

The zoning change will alleviate a threat against hundreds of Prince George's residents who provide day care in their homes who were in compliance with state social service requirements but violated county zoning restrictions on the number of children they were allowed to take care of.

The new law puts no restrictions on the in-home day-care operators who comply with the state regulations.