From now on, fewer city employees will be able to obtain the parking placards that allow parking in restricted zones, a move that will lower road congestion and cut down on the high abuse rate of the placards, Mayor Bloomberg said yesterday.

City agencies must take inventory of the placards they’ve issued before they are forced to reduce their allotted count by at least 20% by March 1, Mr. Bloomberg said. A multi-agency working group will review existing parking-space allocations and on-street parking regulations to study how the spaces can be better utilized for traffic patterns.

“Placards are a necessary tool for conducting city business, but we have no tolerance for their abuse, which contributes to congestion,” Mr. Bloomberg said in a statement.

Only the city’s police and transportation departments will have the authority to issue the permits, and the police department will create a new enforcement agency to ensure compliance, the mayor said. Agencies will also be responsible for creating their own enforcement procedures.

The mayor’s office estimates that there are now 70,000 city-issued permits. An estimate from Transportation Alternatives puts the number at 150,000, which includes counterfeit and expired placards and commuting data figures.

Community organizations have long lobbied the city to regulate the placards because so many employees use them for commuting purposes instead of strictly for work-related business, a spokesman for Transportation Alternatives, Wiley Norvell, said.

“This is one of the worst abuses of government in New York City,” Mr. Norvell said. “Government workers commute at twice the rate of everyone else because they have free parking at the other end, in the form of one of these placards.”

Transportation Alternatives conducted a study in early 2007 that found that three-fourths of the permits are used illegally, with drivers blocking fire hydrants, bus stops, crosswalks, and parking on sidewalks, Mr. Norvell said.