The Senate Appropriations Committee yesterday followed the lead of its D.C. subcommittee and approved the city's $1.5 billion operating budget virtually as the city requested it -- including a record-high $296 million federal payment.

In approving the fiscal 1981 budget, committee members apparently agreed with the new policy of D.C. Appropriations subcommittee Chairman Sen. Patrick J. Leahy (D-Vt.) to give the District "as much flexibility as possible" in running its own affairs without the traditional line-by-line review of the city's budget. In return, Leahy said, the city will have "no excuse for failure to plan accordingly," and city officials must be able to later justify all expenditures to congressional auditors.

With that new hands-off policy in mind, the full committee yesterday tabled a measure that would have forced the city to hire 280 additional police officers. The measure, introduced by Sen. Charles McC. Mathias (R-Md.), was identical to a provision in the House version of the D.C. appropriation that instructs the city to keep its police force at no fewer than 3,880 officers.

The city's police force is currently at 3,600, after the abrupt retirement in August of some 260 officers taking advantage of liberalized retirement benefits. Mayor Marion Barry wanted to reduce the size of the force even further to save costs, but House members, apparently alarmed by reports of increasing crime on Washington streets, instructed the mayor not to reduce the force below 3,880 without congreggional approval.

The difference between House and Senate views on police manpower levels sets the stage for a confrontation once the full Senate votes on the total appropriations bill, and the two sides go into conference. No conference date has been set, even though fiscal year 1981 begins Oct. 1, since the Appropriations Committee still has other pending business before the full Senate acts.

"It (the police force policy) will be a major issue in conference, I'm sure," Leahy said. "Nobody in here is anti-law enforcement. But I really want to move us away from item-by-item telling the city what to do."

Leahy said he personally favored language setting a strength level for the city's police force, "but it goes contrary to what we're trying to do this year." Committee members voted 6-to-5 to table Mathias' proposed amendment, only after Leahy's assurance that he "will personally follow very carefully what is happening in the police department."

Barry, who attended yesterday's Senate panel meeting, said afterwards that his administration would "resist . . . to the end" attempts to restrict his power to reduce the police force level. "We think we have the right to decide where people work and how many people work," Barry said.

Leahy's new noninterference policy also convinced the committee to table a second amendment that would have added language prohibiting the city from using federal funds for abortions. The abortion language was included in last year's D.C. appropriation, but was dropped in the Senate version this year.

After the committee meeting, Leahy called it "superfluous" to include language prohibiting the use of federal money for abortions, since such expenditures are already illegal under federal law. "I have no objection to language that says the District must follow federal law in spending federal money," Leahy said. He said, however, that some abortion language would probably be restored in the upcoming House-Senate conference committee.

Despite the apparent acceptance of Leahy's stated new policy regarding District affairs, the committee nevertheless voted against funding sought by the city for a second campus for the University of the District of Columbia.

Congress had already authorized UDC to use $57 million in capital funds, but the university was required to get congressional approval for whatever plan it drew up to spend that money. UDC trustees have been intent on building a second campus downtown at Mount Vernon Square despite the fact that the school is reported facing declining enrollment and a shrinking city population.

Leahy told the committee he personally opposed UDC's two-campus plan, but said he had promised the trustees "that if this is what they want, I will introduce it and vote for it." The two-campus plan failed by a 7-to-4 vote.