Rep. Norman Y. Mineta (D-Calif.), one of the main congressional supporters of airline deregulation, said yesterday that the Transportation Department "has panicked and over-reacted" to flight delays with a regulatory remedy that imperils competition and threatens higher fares.

Further, he said, the department's Federal Aviation Administration is not meeting its promises to restore the air trafffic control system to full capacity because it miscalculated and did not hire enough controllers to replace those who struck three years ago and were fired by President Reagan.

Mineta is chairman of the House Public Works and Transportation subcommittee on aviation and his views are influential. His criticism echoes complaints from such new airlines as People Express and Southwest.

They come as the FAA is seeking to wrest schedule adjustments from the airlines to ease delays at six major airports. If voluntary agreements cannot be reached, the FAA intends to impose solutions.

Tentative agreements had been reached or were near late yesterday at five of the airports -- Atlanta, Chicago, Denver, New York LaGuardia and New York Kennedy. Difficult discussions were continuing about Newark Airport and both industry and government officials privately questioned whether a voluntary agreement is possible there.

DOT spokesman Mari Maseng, responding to Mineta's charge, said that the FAA action "is not a step toward reregulating the economics of commercial aviation. The scheduling discussions now under way are progressing well, and it is our hope that the airlines will quickly complete the process. At that point, the FAA will have the very limited responsibility for seeing that the agreements are implemented."

According to the FAA's regulatory proposal, once agreements are reached or imposed, the FAA will "prohibit all operators from changing the schedule times of arrivals and departures from those schedules agreed to" during the meetings.

Mineta's comments came in a luncheon speech to an FAA technical symposium. He stressed that he had no problem with the airline meetings as a short-term method of resolving a problem. However, he said in an interview, he is concerned that agreements that freeze airport access to existing carriers are essentially anti-competitive.

If, for example, LaGuardia is declared full and the schedule cannot be changed, it would be impossible for a new carrier to enter the market and offer cheap fares. In his speech, Mineta said, "Having failed to provide an adequate controller workforce, and caused the public to suffer from increased delays, the administration now proposes to compound the misery it has created by depriving the public of competition."

The airline discussions at Newark are instructive. Newark, once the least-used New York area airport, has become a hot ticket with the advent of People Express, which has more than 300 flights into the airport each day, offering cheap fares throughout the Northeast.

In schedule proposals for November, both Eastern Air Lines and New York Air are planning to expand at Newark. John R. Ryan, FAA air traffic operations manager, has told the airlines the FAA wants no more than 68 flights an hour at Newark, although he stressed that that number is flexible.

It may not be flexible enough. For example, between 8 a.m. and 9 a.m., carriers had 106 departures and arrivals scheduled when they began discussions yesterday. By late afternoon, they had moved only 10 flights into adjacent hours, leaving only 28 to go.