Fire department employees regularly use invalid parking placards - issued by their unions - to park illegally outside FDNY headquarters in downtown Brooklyn, the Daily News has found.

Last Tuesday, The News spotted 30 vehicles with invalid placards parked illegally on Gold St. between Myrtle Ave. and Willoughby St.

On Aug. 11, in the same location, The News counted three dozen cars with invalid placards parked illegally.

Officials in Mayor Bloomberg's office and at the Department of Transportation reviewed photos of The News' findings and confirmed the placards are not authorized by the city.

"They are not valid," said Stu Loeser, the mayor's press secretary. "The mayor believes nobody should be parking illegally or inappropriately."

A Department of Transportation representative described the union-issued placards as "illegal" and insisted "they shouldn't be displayed" in government employees' cars.

NYPD Assistant Chief Michael Collins said any government employee parked illegally with an unauthorized placard is "subject to enforcement action."

While the department was unaware of the problem The News found outside FDNY headquarters, he said the NYPD will "take corrective action" if needed.

FDNY spokesman Frank Gribbon said, "We are committed to cracking down and have cracked down" on illegal parking near headquarters.

"I've gotten numerous memos about it," Gribbon said. "Cars are subject to tow - these messages have gone out repeatedly."

On Tuesday, none of the 30 cars illegally parked with invalid placards was ticketed. Six of those cars were on the sidewalk, which would have been illegal even if the cars had valid placards.

An FDNY employee, who would not give his name, told The News that the police typically "extend the courtesy" to government officials to park illegally outside Fire Department headquarters.

"They've been doing it for eight, nine years," he said of the illegal-parking privileges. "Everyone who works here comes and parks here."

Union officials acknowledged the placards do not afford their members any special parking privileges and that their members are aware of that.

"We issue them to identify our members and their personal vehicles - they are not denoted for any other reason," the Uniformed Firefighters Association said in a statement.

The UFA and a spokesman for the paramedics union complained that the department does not issue vehicle-identification tags to all its employees.

In recent weeks, The News found state court employees illegally parking on a Chinatown sidewalk and double-parking near the Bronx courthouse, winning the praise of Bloomberg who said the newspaper is "doing a great service" by "pointing out abuses of the system that should not be allowed to happen."

Matthew Roth, an official with the Transportation Alternatives advocacy group said, "This blatant abuse of power and privilege will continue until the mayor puts a stop to it."