This Feb. 3, 2012 file photo shows the current Federal Bureau of Investigation (FBI) headquarters in Washington. The General Services Administration (GSA) last year announced plans for the FBI to leave the crumbling building. (Manuel Balce Ceneta/AP)

A Fairfax County official is fuming over a proposal by Metro that he says could give the jurisdiction’s rivals in Prince George’s County an unfair advantage in the fierce bidding to land the FBI headquarters.

The proposal would allow the FBI to build its headquarters on 78 acres Metro owns at the Greenbelt station.

In a letter Thursday, Fairfax County Supervisor Jeff C. McKay (D-Lee) criticized the move, saying it “makes it look as if [Metro] is engaging directly on behalf of a particular jurisdiction. By offering the land at the Greenbelt site to the FBI, Metro clearly appears to be intentionally entering the debate — one that is high stakes and that is playing out among its very funding partners.”

The General Services Administration (GSA) last year announced plans for the FBI to leave the crumbling, brutalist behemoth that is the District’s J. Edgar Hoover Building, setting off an intense competition among jurisdictions across the Washington region to try to lure the bureau and its thousands of jobs.

The GSA has proposed swapping the Hoover building site for a new headquarters on at least 40 acres near a Metro station and the Capital Beltway.

On Thursday, Metro’s real estate committee voted in favor of allowing a developer to exercise rights to work with Prince George’s to compete for the FBI headquarters.

McKay’s letter to Metro officials accused them of “taking sides in a process that should be impartial and fair.”

Jim Herbert, business development manager at the economic development department in Loudoun County, which also hopes to become the FBI’s new home, said he doesn’t see how Metro can claim impartiality in light of the proposal.

“Are they going to come up with an equivalent offer for Montgomery County?” he asked.

McKay suggested that Metro’s actions could have financial consequences: “This is an extremely imprudent move at a time when [Metro] is seeking — and needs — substantial additional funding from all of us.”

Fairfax has proposed moving the FBI to a site in Springfield near the Franconia-Springfield Metro station that houses large, federally owned storage warehouses that are well past their prime. The county has long hoped to redevelop the area.

Metro said it is not taking sides and is willing to work with any jurisdiction on a deal that would benefit the transit agency’s mission. Metro spokesman Dan Stessel said Thursday that the agency is “agnostic” as to what location the FBI chooses: “There is no preference for one jurisdiction over the other.”

Prince George’s says that moving the FBI there would help relieve Beltway congestion and spur economic development in a less-affluent part of the region. The county has the least federal office space of any major local jurisdiction. Responses to the GSA’s search for a new FBI site are due March 4, after which the GSA may seek more detailed proposals.

Dana Hedgpeth contributed to this report.