Three major Northern Virginia landlord and developer organizations signed voluntary pledges yesterday to aid tenants in buildings slated for condominium conversions, but some tenants' rights groups were dubious that the promises would serve any purpose.

"They're not giving us anything," said Larry A. Miller, president of the Woodlake Towers Tenant Association, shortly after representatives of the Northern Virginia Builders Association, the Condominium Developers Association, and the Apartment and Office Building Association signed the agreement with the Fairfax County Board of Supervisors.

"They're saying if it suits their needs -- if it looks like it will be advantageous to them -- they'll do something. Otherwise, forget it," said Miller.

The agreements set guidelines for the organizations' members to follow in condominium conversions and include a promise to "endeavor" to provide special purchase and lease programs to assist tenants who want to remain in their apartments. The guidelines, similar to ones developed by Arlington and Alexandria authorities, also specify that building owners also will "endeavor" to provide relocation help for displaced tenants, as well as financial help for displaced lower-income tenants.

Fairfax Supervisor Audrey Moore, whose Annandale district contains many rental units that are being converted to condominiums, yesterday said that the guidelines cannot be legally enforced. "It's just so much applesauce," she said.

County Board Chairman John F. Herrity said, however, that he was hopeful that "moral suasion" would encourage widespread conformance to the Fairfax guidelines. "I'm sure that 95 percent of them will go along with it, and the other 5 percent probably wouldn't obey even if you had a law," Herrity, a Republican, said.

"And I think that other 5 percent will have a heck of a time operating in this country. Let's lay it on the line."

But Moore, a Democrat, said the agreements amounted to "the best of bad alternatives" because Virginia law prohibits local jurisdictions from imposing any requirements that condominium developers lend assistance to tenants.

Virginia law provides only that tenants must be notified of impending condominium conversions at least 120 days in advance, and recent efforts to attach more stringent provisions to protect the rights of tenants largely have been rejected by the state legislature.

Fairfax County last year experienced the Washington area's greatest percentage increase in rental units converted to condominiums. The 2,390 unit percentage increase in rental units converted to condominiums. The 2,390 units converted there represented a 60.9 percent jump over the previous year.

The lack of regulation in Virginia contrasts with extensive condominium rules in the Maryland suburbs and in Washington. In the District, a developer may not convert a building to condominiums without a majority vote of its tenants, a developer may not evict elderly, lower-income tenants, and a developer must make financial payments into a housing assistance trust fund.

Spokesmen for the developers said they were hopeful that the agreement, which was drafted by representatives of the three groups and a country board subcommittee, would do much to improve the industry's image. "Regardless of what state law requires, we will work with tenant groups to help them either move or find a place in the community," said Samuel Finz of the Condominium Developers Association.

"We're going to police our own industry rather than face the restrictive requirements that a local government can impose on us."

Industry spokesmen rejected criticism by tenant groups that had been angered at being left out of the guideline effort. "Tenants could contribute little to the process," said John O'Neill, executive vice president of the Apartment Owners and Office Building Association.