Senior Metro officials yesterday accused the Reagan administration of breaking promises that the new 5-cent-a-gallon federal gas tax would bring a significant increase in federal transit aid nationwide in fiscal 1984.

"Either advertently or inadvertently, the administration lied to the entire transit industry on the impact of the gas tax," D.C. transportation and public works director Thomas Downs said yesterday.

His remarks came at a meeting of the Metro board's budget committee, where board members were told that President Reagan's draft 1984 budget would give Metro federal capital and operating aid of $305 million, $46 million below this year's $351 million.

Downs, one of the District's two Metro board members, said administration officials seeking for support for the gas-tax increase last year promised the tax would mean more federal aid for transit, not less. The revenues from one cent of the tax increase are reserved for transit.

Metro General Manager Richard S. Page said after the meeting that federal funding proposed for Metro in fiscal 1984 would necessitate "devastating cuts" in subway construction, operating subsidies and programs to increase bus and rail reliability. "I think it's outrageous," he said, labeling the administration's proposal a "breach of faith."

The protests appeared to be the opening volley in Metro's annual battle for money on Capitol Hill. Reagan's budget, which would pare transit programs nationwide from $3.9 billion this year to $3.8 billion in an effort to reduce the deficit, is only a proposal and can be altered in Congress.

In fiscal '84, Metro hoped to draw $300 million from a special $1.7 billion fund that Congress created in 1979 for Metrorail construction. But the administration wants Metro to take only $230 million, though it promised to look for an additional $20 million from some other source.

Metro officials say the tax bill, which was backed by the administration, called for Metro to get a block grant of $75 million in fiscal '84. Metro had planned to use it to buy new buses and rebuild old ones, improve bus garages, tighten maintenance and pay operating deficits. None was to be spent on subway construction.

However, the president's draft budget shows only $55 million for Metro's block grant and suggests that the agency use $25 million of it for subway construction. That would leave only $30 million for the other programs for which Metro had expected $75 million.

In other business, staff members briefed the committee on testimony heard at public hearings on the fare increase proposed for April 2. Speakers criticized many facets of the proposed increase, the committee was told, but raised no new arguments against it.

Metro planner Robert Pickett said the staff expected to recommend that the board adopt the package with few changes. The package would raise most base fares to 75 cents, increase mileage fees subway riders pay at rush hour and raise special fares for elderly and handicapped riders and some fees for riding buses across zone lines.