Fairfax County Executive J. Hamilton Lambert's proposal to spend $14 million next year for preliminary work on a sprawling new government center west of Fairfax City has revived a volatile issue that long has divided the county's leaders.

But the project, which would be the costliest investment ever made by the county in the proposed complex, may fall victim to an issue with far more political appeal: cutting taxes.

The executive's proposal, part of his $1.25 billion budget, calls for building roads and water and sewer lines at a county-owned, 183-acre tract near Fair Oaks Mall, the site for the proposed complex.

Many of the county's nine supervisors have gone on record as promising to cut the county's real estate taxes and some yesterday expressed puzzlement at the thought of spending $14 million on a project that may never get built.

"Where's the board going to find the money for a tax decrease?" asked Supervisor Joseph Alexander (D-Lee). "I have favored the new government center and voted for it on a number of occasions, but I don't think it's high enough on my priority list to support $14 million" for improvements to the site.

Most supervisors say they are eyeing a decrease of 5 cents or more in the real estate tax rate of $1.46 per $100 valuation. Installing roads and sewers for a project that some have called "a monument to bureaucracy" isn't nearly as popular, they say.

A 5-cent reduction in the tax cut would mean slashing about $15 million from Lambert's budget. With a price tag of $14 million, the construction recommended by Lambert at the proposed government center may be a likely target for savings when supervisors start trimming the budget in April. The executive has defended the proposal, saying the county can recoup the $14 million by reselling the site if the county decides against the new complex.

Lambert's proposal, however, effectively forces the board to deal with the long-simmering issue of moving the county offices out of Fairfax City. "I think it's going to be a real tough battle," said Board Vice Chairman Martha V. Pennino, a leading supporter of the complex.

The government center, which opponents have called "an edifice complex," has been on the county drawing board since a blue-ribbon commission endorsed the idea in 1978. Estimates for the cost of the complex, which would supplement the current 12-story administration building and courthouse, range from $55 million to $72 million.

Most of that cost would probably come from a bond issue, but supervisors have never put the center up for a vote.

Supporters of the new center, including Lambert, have said the facility would save Fairfax taxpayers money. The county spends about $4 million a year to rent office space from private landlords throughout the county, according to general services director Fred K. Kramer.

The overflow into private office space has grown as the county's bureaucracy has more than doubled, jumping from about 3,000 people in 1970, shortly after the current administration building was completed, to an estimated 7,900 next year.

Moreover, advocates of the new center say, the county could recover thousands of dollars in taxes now paid to the Fairfax City government by businesses that would move to the Fair Oaks area if the county administration building is relocated.

"The economic argument for a new complex is just overwhelming," said Michael S. Horwatt, the lawyer who chaired the first relocation study in 1978. He says Lambert's proposal to spend $14 million in preliminary work "has to rivet attention on the fact that something has to be done.

"He's saying: 'Look, don't fool yourself . . . you're spending money on an administrative complex. The only question is whether you're spending it on rent or on a new facility."

Opponents of the center, on which the county has already spent more than $4 million for land acquisition and architectural work, insist it has little popular support, particularly in a political season dominated by talk of tax cuts and new roads.

The board, which plans to propose a road bond issue of up to $80 million at a referendum in November, is unlikely to clutter the ballot with a multimillion proposal for the government center. CAPTION: Picture, J. Hamilton Lambert . . . $14 million plan stirs controversy; Map, Proposed Government Center. By Dave Cook--The Washington Post