Former Fairfax County purchasing director Charles J. Cedeno sued the county yesterday for more than $1 million, charging that he was fired for "daring to expose" what he sees as a pattern of irregularities within the $50-million-a-year contracting agency.

County officials offered to let Cedeno resign as long as he did not make his allegations public and did not hire a lawyer to fight his ouster, according to the suit filed in U.S. District Court in Alexandria.

When Cedeno did talk to reporters this summer, the county fired him on the grounds that he used vulgar language at work and intimidated his co-workers, the suit says.

County officials have said Cedeno's ouster was unrelated to his criticism of county purchasing practices and did not result from the publicity about his allegations. The Board of Supervisors fired Cedeno in late June after county officials said interviews with 32 current and former county employes revealed that his allegedly vulgar style created "an atmosphere of fear and disgust" in the purchasing agency.

A county spokesman declined comment on the suit yesterday, saying the county had not yet received a copy.

Should the suit survive the county's almost certain efforts to have it dismissed, it could result in a public court battle between Cedeno and the county over his repeated claims of mismanagement and irregularities within the purchasing agency.

An independent audit of the department, conducted in response to Cedeno's allegations, concluded last month that the county is operating in compliance with the letter of state and county purchasing regulations. The study criticized some county purchasing rules as vague, and it appeared to corroborate Cedeno's allegations that proper purchasing procedures had not been followed in the awarding of at least four county contracts the last two years.

Cedeno has charged that major county contracts were awarded without competitive bidding, that the county permitted cost overruns of up to 10 percent above county contracts with little or no scrutiny, and two county supervisors did not follow purchasing procedures in buying office furniture.

In his suit, Cedeno further alleges that several unidentified supervisors complained to his superiors that his actions as purchasing director were "unnecessarily annoying their friends, who also happened to be contractors."

County department heads' alleged efforts to "steamroll requisitions . . . were dangerous and could lead to corruption as well as, in fact, wasting enormous sums of county funds by awarding contracts to favored contractors instead of awarding them to the lowest bidder," the suit says.

In asking the courts to reinstate him with full back pay, Cedeno, 44, says in his suit that the county violated his constitutional free-speech rights and did not follow due process when they fired him, and that county officials slandered him by publicly detailing the reasons for his dismissal.

No trial date has been set.

Meanwhile, in neighboring Prince William County, state police have started an investigation into allegations of irregularities and questionable bidding procedures in that county's purchasing agency. The state police were called in by chief prosecutor Paul B. Ebert after a businessman complained that a county bid request was improperly written.