A key committee in the Democrat-controlled Virginia Senate has proposed a congressional redistricting plan that would have cost Rep. Stanford E. Parris his seat had it been in place last November.

Parris, a Fairfax Republican who narrowly unseated three-term Democrat Herbert E. Harris, criticized the plan yesterday as the work of Christopher J. Spanos, Harris' former administrative aide, whom Parris branded "a liberal former union organizer."

The redistricting proposal, sponsored by state Sen. Adelard L. Brault (D-Fairfax), would split Prince William County between Parris' 8th and Rep. J. Kenneth Robinson's 7th districts. Under Brault's plan, eastern Prince William and northern Stafford County would remain in the 8th along with southern Fairfax County and Alexandria.

A study of last November's election results shows that Parris rolled up a 2,600-vote plurality -- more than enough to account for his winning margin of 2,100 votes -- in 14 western Prince William precincts that would be moved out of the district.

"On balance," Harris said yesterday, "the proposal would make the 8th District a little more Democratic. . . . We've got to move those folks somewhere."

The district's boundaries must be redrawn because 1980 Census figures show that the 8th District's population is about 52,000 greater than the ideal population of 534,628 required under the one-man, one-vote edict of the Supreme Court.

Del. Elise B. Heinz (D-Arlington-Alexandria), a member of the House Privileges and Elections Committee, predicted the Brault plan will pass easily when the legislature meets in a special session next week. Heinz, who stands to lose her own legislative seat because of population shifts, said the congressional proposal "is not partisan. If you look at the map, that's the logical place to cut it [the 8th] off."

Sen. Hunter B. Andrews (D-Hampton), chairman of the Senate Privileges and Elections Committee, also disavowed any partisanship. "I don't know anything about partisan considerations up there [in Northern Virginia]. All I know is that we're talking about 50,000 people."

Harris, who now practices international law in Washington, is so certain to challenge Parris in 1982 that he has not even closed his 1980 campaign headquarters, and Spanos works there when he is not in Richmond.

Harris noted that the adjoining 10th District is "virtually the ideal size. It shouldn't be tampered with." That is the position that the Senate committee has reportedly agreed to adopt, making Parris the only Northern Virginia congressman whose district should be affected by the new census.

The 10th District seat also was captured by a conservative Republican, Frank Wolf, who unseated three-term liberal Democrat Joseph Fisher. It is not known if Fisher will challenge Wolf next year.

Parris said yesterday he is a "nowin" position, because he does not want to suggest moving anyone out of a district he recaptured after a six-year hiatus. He said he is staying out of the fight because "It's the legislature's job. Those guys are capable of doing it without outside interference. But it shouldn't be determined on a conservative or liberal basis. I don't want Spanos to be architect."

Spanos, contacted in Richmond where he is directing the campaign of Democratic lieutenant governor hopeful Richard Davis, said he was "merely advising the Democratic senators from Northern Virginia. I was working with whatever they wanted. I was hired by Abe Brault, and he very much knows his own mind."

Parris said "the guidelines are clear" and that the redrawn districts must be contiguous, numerically equal and maintain a community of interest. Splitting Prince William County between east and west, Parris said, "exacerbates the competitiveness" between the population centers of Woodbridge in the east and Manassas in the west.

Spanos responded that the county's growth "has been along radial patterns, and it may be unfortunate, but there are two distinct communities of interest."

Parris declined to say how he would redraw the boundaries, except that it should be done "around the edges" of the district. He said he may discuss his concerns with Republican Gov John N. Dalton, but said he is prepared to "live with whatever I get. Obviously, I'll have to.