Energy Secretary James R. Schelesinger Jr. yesterday sent to Congress legislation he said would reduce the time it takes to license and construct nuclear power plants to 6 1/4 years from the 11 1/2 years it takes today.

"The purpose of this legislation is to provide stability and predictability to the licensing process," Schelesinger said at a news conference. "The nuclear licensing process cries out for reformation."

The legislation was immediately criticized yesterday be several environmental and nuclear groups, who charged that it would discourage public participation in the licensing process and endanger the environment.

The first comprehensive legislation introduced to set guidelines on nuclear licensing, the bill would allow states and electric companies to select a plant site before the licensing procedures began, to choose from a standard plant design and to win a construction permit and an operating license at the same time.

Schelesinger said that today's siting and licensing process adds as much as $600 million to the construction costs of a nuclear power plant, largely through inflation and interest rates on bank loans that accrue from construction delays.

"The overall result is to add 3 to 3.5 mills per kilowatt-hour to consumer electric costs," Schelesinger said. "That means an estimated $30 a year to consumer's electric bill."

In a ringing defense of nuclear power, Schelesinger said that while there have been "disputes and obstacles" to the nuclear generation of electricity, "the realities are" that automic energy provides 13 percent of the electricity in the United States. Schelesinger said nuclear electricity capacity alone is greater than the entire nation's conventional capacity during World War II.

The Natural Resources Defense Council, the Environmental Policy Institute and Ralph Nader's Critical Mass energy project all opposed the Schelesinger plan. Critical Mass said the legislation would "discourage public participation in regulatory hearings and cause deep potential harm" to the environment.

"More important," Critical Mass, an antinuclear group said, "the proposed changes incorrectly diagnose the cause of the delay in the licensing process. Every independent study of the matter shows that manufacturing defiencies, late equipment and labor problems" are the main cause of nuclear plant delays.

Rep. John D. Dingell (D-Mich.), chairman of the subcommittee on energy and power, said he was concerned that the licensing proposal might weaken the National Environmental Policy Act by transfering to the states federal responsibilities for siting reviews.

Dingell said the bill "would make the state environmental determinations final and not subject to challenge before the commission or a federal court. The federal responsibilities in this area are clear and must not be compromised."

In the bill's defense, Schlesinger said he is proposing that the states take over the role of siting nuclear power plants "as they must." He said the Energy Department will introduce companion legislation that would produce federal funds for the states to plan their electrical needs "in accordance with their own needs."

The NRG and the Environment Policy Institute echoed the concerns of Critical Mass. The EPI blamed the delays in nuclear construction "on manufacturers and labor unions." It said that in the period 1967 to 1976 manufacturers were responsible for 154 delays and labor unions for 142 days cut of 419 individual delays.

Schlesinger said it now takes four years to choose nuclear plant sites before construction begins. He said that it is his hope under this legislation to "preselect" a site and "bank it" so that construction can begin one year after a site is approved.

The construction period, Schlesinger went on, can be reduced to 5 1/2 years from present 7 years. One way to eliminate delays is to limit the issues that can be challenged during construction "health and safety" issues that were not involved in the siting process.