Richmond's chief prosecutor accused Virginia Attorney General J. Marshall Coleman yesterday of usurping his authority to initiate criminal charges against a firm suspected of rigging bids on safe highway contracts.

The prosecutor, Aubrey M. Davis, said the company, Central Contracting Co. of Farmville, Va., may have gotten a "good deal" in a civil settlement it reached with Coleman's office last week.

Davis said the language of the settlement does not prevent Davis or prosecutors in other localities where bid-rigging might have occured from instituting criminal charges. Under state law, the attorney general has "no legal authority to waive local prosecution." Coleman said "I couldn't, even if I wanted to," he said.

Coleman, the leading Republican contender in next year's governor's race, said he is convinced that Democrat Davis' comments were politically motivated.

In response to criticism of the settlement voiced by Davis and other local Virginia prosecutors, a legislative study commission has appointed a five-member subcommittee to look into the agreement, according to state Sen. Stanley C. Walker (D-Norfolk).

Walker, chairman of the Virginia Crime Commission, said the panel wants to find out more about the agreement and has not yet reached any conclusions. "We do not want the thing to get into the political arena," Walker said. Four of the five legislators on the special subcommittee are Democrats.

The $50,000 settlement agreed to by the state and Central last week was a penalty for what state officials said was collusive bidding on five state highway department contracts during a two-year period. The settlement came two days after Central was fined $125,000 in federal court for a case in which it pleaded guilty to bid-rigging charges involving a Richmond airport paving contract.

Central admitted no wrongdoing in the agreement with the state.

The Virginia agreement permits Central to resume bidding on state highway contracts after being suspended from the department's approved bidders list for three months.

Prosecutor Davis, in critizing the agreement, called attention to a section that reads, in part: "the commonwealth . . . agrees not to sue or prosecute Central . . . (for) criminal or civil laws proscribing conspiricy, collusion or schemes or acts to defruad . . ."

"The agreement," Davis said, "is the best evidence.It speaks for itself."

"I think anytime you avoid criminal responsibility, and if that happens here [in Central's case] of course, I think you've gotten a good deal," Davis said. He added that his office still plans to look into the possibility of filing criminal charges, but he said he believes the agreement usurped his authority to do so.

Coleman's investigation into possible antitrust violations on state highway contracts was launched as a follow-up to a wide-ranging federal criminal probe into bid-rigging.