An independent audit of alleged irregularities in Fairfax County's purchasing department has failed to turn up evidence of serious wrongdoing, but leveled criticism at numerous county guidelines and procedures, the county's supervisors were told yesterday.

The audit conducted by longtime county auditor Peat, Marwick, Mitchell and Co., concluded that the couunty's $50-million-a-year purchasing agency is operating in compliance with the letter of state and county purchasing regulations.

The study criticized some county purchasing rules as vague and overbroad, and concluded that county regulations often do not offer purchasing agents sufficient guidance in areas such as competitive bidding, negotiated procurement and public advertisement for bids.

Former chief county purchasing agent Charles J. Cedeno, who was fired by the board two weeks ago after associates complained about his use of vulgar language in the office immediately labeled the audit a "whitewash."

"Why did they stop there?" asked Cedeno, who claims his firing was part of a county effort to silence his allegations that mismanagement in the purchasing department was costing county taxpayers millions each year. "It was politically influenced. They don't want any scandal because their bond rating would come down."

Members of the county board of supervisors who received the report in public session yesterday, obviously were pleased at its findings but resisted the urge to claim to claim it as a victory.

"We're conducting ourselves consistent with state law." said Board Chairman John F. Herrity, a Republican. "However, if you take higher standards, we could do a better job -- and there is no question in my mind that this will be done."

Late in the day, the board voted unanimously to instruct county staff members to draw up recommendations for upgrading and tightening purchashing procedures, along the lines specified in the audit report.

Although the Peat, Marwick, Mitchell & Co. autid did not mention Cedeno by name, it appeared to corroborate allegations by the former county official that proper purchashing procedures had not been followed in the awarding of at least four county contracts over the past two years.

The audit reported that:

The clerk of the Fairfax County Circuit Court, James E. Hoofnagle, ordered and received about $39,000 worth of microfilm equipment before the county had sent out for bids on the contract.

The County Community Services Board ordered $3,000 worth of furniture without seeking competitive bids or consulting the county's purchasing department.

The county's Economic Development Authority negotiated $11,800 worth of contracts to set up a business exhibit without seeking competitive bids or consulting the purchasing department.

The county's Office of Manpower arranged for a six-month lease on 10 word-processing machines, at a cost of $25,000, without seeking competitive bids or obtaining authorization from the purchasing department.

In each case, auditors said, no county funds were disbursed on the contracts until the purchases were authorized by the Board of Supervisors in accordance with state law.

Reviewing a random sample of 99 files on contracts of more than $2,500 each, auditors could find no evidence that 76 of them had been advertised for bidding on local newspapers, as required by state law.

Purchasing chief Fred K. Kramer said that the county's system of advertisements for bids had been formalized last fall, midway through the 18-month period examined by auditors, and that since then the problem had been eliminated.

Eighty-five of the 99 files contained documentation that the county had solicited bids from more than one vendor, but 14 of the contract files indicated that a bid was solicited from only one vendor. Four of those files had documents giving reasons for only soliciting one bid, the auditors said, but the remaining 10 offered no such documentation.

State law requires county purchasing agents to solicit competitive bids on major contracts through the use of mail and public notice boards.

The auditors concluded that, while the county is making an effort to ensure competitive bidding for proposed contracts over $2,500, "similar efforts to secure the same level of competition for proposed acquisitions under $2,500 were less evident." They urged that the county better define the required level of competition, and hold seminars for county employes to ensure all are aware of proper purchasing procedures.

Board chairman Herrity reacted angrily yesterday to suggestions that the board had used poor judgment in selecting Peat, Marwick, which had handled most of the county's outside auditing business for more than a decade.

"It's absolutely ridiculous to think that Peat, Marick would prostitute itself for $20,000," Herrity said.

The board also voted to create a three-member committee to review procedures through which county employes can "blow the whistle" on alleged county improprieties. The supervisors said they wanted to allay fears of employes who might be intimated by the storm over Cedeno's allegations and subsequent firing.

That vote came after Herrity stated publicly his belief that accounts of such fears were vastly overblown by inaccurate media reports.

"I think its time to deal with the facts, which I know is unusual for the media to get involved in," Herrity said. "The fact is that Mr. Cedeno was fired for reasons completely unrelated to these charges . . . To call Cedeno a whistleblower is a perversion of the term whistleblower."