Ten of the nation's largest conservation groups yesterday issued an "indictment" of the Reagan administration for imperiling public health and natural resources, focusing their combined attack for the first time on the president instead of his subordinates.

"The president and his officials are engaging in a wholesale giveaway to private interests of our most precious natural resources," concludes the 35-page report, which summarizes 220 administration policies on pollution control, toxic wastes, natural resources and energy development. It alleges that Reagan policies are systematically dismantling a decade of effort to protect the environment.

"In the name of 'getting the government off our backs,' they are giving away our natural heritage," the report says.

The report represents a significant shift in political strategy by the environmental movement, which until now has focused opposition largely on the Reagan Cabinet members championing the most dramatic changes, but not on the president. Last year the groups gathered 1 million signatures on petitions calling for the resignation of Interior Secretary James G. Watt and delivered them to Congress amid much publicity.

But the groups "saw a real pattern develop" in policies emanating from several agencies, the Wilderness Society's Ed Norton said at a press conference. "It isn't Environmental Protection Administration chief Anne M. Gorsuch and it isn't Assistant Agriculture Secretary John Crowell and it isn't Watt and it isn't Energy Secretary James B. Edwards. It's Reagan," Norton said.

Both Interior and EPA issued statements discounting the report. EPA called the report "full of exaggerations, half-truths and some outright inaccuracies."

A spokesman for Watt said: "The secretary of the interior will continue to do the job to which he was appointed, as will other officials of the Reagan administration. We would welcome constructive dialogue with organizations having legitimate interests in the development and protection of resources, but we will not be influenced by a small number of special interest groups and their commercial leadership."

Sierra Club President Michael McCloskey noted, however, that the 10 groups have a membership of more than 1 million. Besides the Sierra and Wilderness groups, other sponsors of the report are Friends of the Earth, Natural Resources Defense Council, National Audubon Society, Environmental Defense Fund, Environmental Policy Center, Environmental Action, Defenders of Wildlife and Solar Lobby.

The coalition issued the "indictment" in San Francisco after one of many strategy sessions held since the appointment of Watt. At the press conference, National Audubon Society President Russell Peterson, a former governor of Delaware, accused Reagan of trying to undo a decade-long, bipartisan congressional effort to curb pollution.

The groups will distribute about 7,000 copies of the report to Congress and citizens' groups across the country who, according to Norton, "may not know what the administration's real environmental policies are."