The Alexandria City Council, in the wake of the resignation in June of Vice Mayor James P. Moran, last night approved a new requirement for bidders on city contracts stipulating that they must sign a form disclosing any business ties to elected city officials or employes.

Democratic Councilman Donald C. Casey, who was a strong critic of Moran three months ago when Moran was at the center of a conflict-of-interest controversy, proposed adoption of the requirement at last night's council meeting. All seven council members voted to approve the measure.

Moran resigned as part of a plea agreement after a special prosecutor charged that Moran had violated conflict-of-interest laws by accepting favors from Peter Labovitz, one of two bidders on the purchase of a valuable city-owned parking lot.

In the past, state law has required that elected officials disclose any business relationship that might qualify as a conflict of interest in city contracts. Under the new city ruling, the requirement is extended to private residents and city employes.

Casey, arguing for the disclosure measure last night, quoted portions of the prosecutor's charges against Moran and suggested that the incident could have been avoided if a similar rule had existed at the time.

The new rule went into effect yesterday before the council voted, based on a decision by city officials that the city had the power to require the disclosure under Alexandria's existing city code.

The council did not set any penalties for businesses that violate the new rule, but it asked that the city attorney's office propose an ordinance including civil and criminal sanctions.