Fairfax County Democrats yesterday accused their Republican counterparts of trying to increase their one-vote advantage on the Board of Supervisors by redrawing the county's eight political districts.

"I think there's no question that redistricting is a purely partisan exercise," declared Supervisor James M. Scott (D-Providence), who is seen as the most vulnerable of the board's four Democrats to a GOP challenge in 1987. Scott, a four-term supervisor, won his last election by a very small margin. "The Republicans say every four years that they're coming after me, and this is just another method of doing that."

Republicans heatedly denied those contentions, saying the redistricting plans were designed to promote a more equitable population distribution among the supervisors, not to tighten their grip on the board, where the Republicans now hold a 5 to 4 advantage.

"I will not be part of any partisan gerrymander," said Supervisor Thomas M. Davis III (R-Mason).

"This isn't being done with the idea of doing Mrs. Moore political damage," added Supervisor Nancy K. Falck (R-Drainesville), referring to Democratic Supervisor Audrey Moore, who represents the Annandale district.

The redistricting, which has been the source of speculation for weeks, arose publicly for the first time yesterday when Board of Supervisors Chairman John F. Herrity denounced a proposed bill in the Virginia General Assembly that would sharply limit the redistricting authority of counties, cities and towns.

The bill, sponsored by state Sen. Hunter B. Andrews (D-Hampton), would prohibit local governing bodies from redrawing ward or district boundaries at any time other than after the U.S. Census, which is conducted at 10-year intervals. The board now has the authority to use state population estimates to redraw district lines every five years.

Herrity, a Republican who is elected at large, charged yesterday that the bill is aimed at Fairfax County for the purpose of protecting the board's four Democrats. "It's designed to keep this county from redistricting," Herrity said during a break in the board meeting.

He also charged that Andrews was fronting for state Sen. Richard L. Saslaw, a Fairfax Democrat who Herrity said was the prime mover behind the legislation. Herrity said that Saslaw "just got one of his buddies to introduce it."

"Jack must be hallucinating," Saslaw said when contacted in Richmond. "I've had no communications with Hunter Andrews on this at all. I don't see what the furor is all about." Andrews was unavailable for comment.

Herrity said he would not be dissuaded by the bill. "We are going to move ahead with redistricting," he vowed. "We're going to fight it politically and in the courts."

Scott, the most likely target of the Republican maneuvering, is an unabashed advocate of liberal causes and has never won with more than 53 percent of the vote. His sprawling Providence district is viewed by Republicans as ripe for a realignment they can defend.

While the GOP board members also may try to carve up Moore's district, they are not expected to go after either Board Vice Chairwoman Martha V. Pennino (D-Centreville) or Supervisor Joseph Alexander (D-Lee).

"Jim and I are the targets of it," Moore said, adding that she was "a little bit nervous" about the prospect of the board's majority rearranging the composition of voters in her district.

Pennino said that although she is not alarmed about what the potential redistricting would mean for her, she believes that partisan motives are driving the Republican efforts. She said that was obvious because none of the Democrats has been consulted about the idea.

In another action yesterday, the board voted to ask the Hazel-Peterson Co. to postpone until early April the hearing on its rezoning application for a proposed commercial-residential development at the Vienna Metro station.

The massive project has encountered severe criticism from Scott and from members of the citizens task force that is drafting a proposed development plan for the area.