An array of Northern Virginia officialdom came here yesterday to plead for passage of a bill that would allow a one percentage point increase in the region's sales' tax to pay for mounting Metro subway operating costs and other mass transportation needs.

The future of the tax bill which already has passed the Senate, is cloudy, however. While there appears to be barely enough votes on the House Finance Committee to send the bill to the full house, some of those lawamkers appeared to be wavering, judging from questions asked during a hearing on the measure.

Three opponents, Fairfax County Supervisor Audrey Moore and two taxpayer association representatives, spoke against the bill, which is expected to generate about $34 million in the first year. Two-thirds of this money would go toward Metro operating costs.

In other developments, a Senate committee killed a House-passed bill that would have voided Fairfax and Loudoun counties ordinances requiring deposits on soft drink containers. And legislation to end the 75-year-old war over an exation between Virginia's cities and counties was declared dead by its sponsor, Del. Thomas J. Michie Jr. (D-Charlottesville).

The one percentage point boost to the state sales tax would result in a 5 percent levy in the five Northern Virginia jurisdictions, equal to that in MAryland and the District of Columbia. However, the revenues from the current 4 percent Virginia sales tax already are greater than the other Washington-area jurisdictions because it is applied to more items, notably food.

In order for the increased tax to be imposed, elected representatives of 90 percent of the 850,000 residents in Fairfax County, Arlington County, Alexandria, Falls Church and Fairfax City would have to request it. Representatives of all but Fairfax City were here yesterday to urge passage of the bill.

Arlington County Board member Joseph S. Wholey said that if the tax were imposed, property and business license taxes in his jurisdictions could probably be decreased. The property tax bill for the average homeowner in Arlington is currently increasing at the rate of $100 a year, Wholey said.

A key focus of questioners' objections is the 90 percent approval provision, which is aimed at preventing a repeat of Fairfax City's single-handed rejection of another regional tax measure. That is a 4 percent gasoline sales tax measure, which requires unanimous approval from all the Northern Virginia jurisdictions. Fairfax City, which combined with Falls Church contains less than 5 percent of the area's population, has refused to go along with the tax.

Sen. Omer L. Hirst (D-Fairfax), sponsor of the increased sales tax measure, said that representatives of 10 percent or more of the 850,000 Northern Virginia residents could ask for the tax to be repealed, and it would be automatically.

Fairfax County Supervisor Martha V. Pennino (D-Centreville) said Metro expenses were now the fifth largest expenditure in the county budget, and that the current $1.74 per $100 of assessed valuation real estate tax there is forcing people to move from the county. Revenue to pay the annual Metro-related costs, which Fairfax County Supervisor Marie B. Travesky (R-Springfield) said will be close to $21 million next year, comes primarily from property taxes.

Moore, objecting to the proposal, said that allowing the Northern Virginia Transportation Commission to administer the tax revenue rather than a "general governing body," was a "serious departure" from traditional Virginia procedure. She also objected to the "way Metro is being managed," and to the provision that would allow the tax to be imposed without the consent of Fairfax City.

"That isn't fair," she said.

The Fairfax and Loudoun bottle deposit laws remained intact when Sen. William E. Fears (D-Accomac) changed his mind overnight and voted against the bill that would have killed local ordinances. Fears, at a Tuesday night meeting of the Agricultural, Conservation and Natural Resources Committee, said he was turned around by a letter he received Monday from Newport News Mayor Joseph C. Ritchie asking him to oppose the bill.

Bottlers and other opponents of the local ordinances have one more possible weapon -- a House joint resolution before the Senate Rules Committee that says "it is the intent and sense of the General Assembly" that "local governing bodies should not enact (such ordinances)." If passed, the joint resolution would not have the force of law, but deposit foes could cite it in their pending suits against Fairfax and Loudoun.

The latest in action, on the apparent annexation issue, failure of the compromise was a blow to Michie, who for seven years has been trying to put together legislation that would win the support of both cities and counties. Cities, losing part of their tax base in the flight to the suburbs, have been putting annexation pressures on adjacent counties and, as a result, relations between localities have been strained and at times hostile.

Early this session, the Virginia Municipal League, which represents cities, and the Virginia Association of Counties announced a compromise that was incorporated in Michie's legislative package. The Michie bills essentially gave the cities extra state aid in exchange for their losing the right to annex parts of urban counties.

While two major parts of the package have passed the House and been sent to the Senate, the bill that would have provided the major portion of the extra aid to the cities wasn't able to survive opposition in the House Appropriations Committee.

After the committee voted 11 to 8 on Tuesday to hold over the money bill, Michie and his staff hastily put together amendments designed to meet objections of legislators concerned about the cost of the measure.

The money bill in its original form would have cost more than $100 million annually by 1982, with adjustments for inflation. To ease apprehensions about that sum, Michie, in his amendments, proposed that law-enforcement aid -- which accounts for most of the money -- be gradually phased in over a 10-year period.

But the gesture was not enough for opponents, who included two of Northern Virginia's three delegates on the committee -- Vincent F. Callahan Jr. (R-Fairfax) and Warren E. Barry (R-Fairfax).

"It's all over," Michie said after the vote.