An Agriculture Department proposal to designate 15 million acres of new wilderness areas drew fire yesterday from environmentalists, the timber industry and oil and gas companies.

The proposal, if approved by President Carter and Congress, would almost double the size of the nation's wilderness system but a jo-nt statement by the Sierra Club, the Wilderness Society, Friends of the Earth and the National Audubon Society expressed "acute disappointment" with its size.

On the other side, the National Forest Products Association said the proposal would reduce the amount of commercial timber available for building homes. The Rocky Mountain Oil and Gas Association said important energy supplies would be cut off.

The department also proposed to open for development more than 36 million acres that had been in limbo since 1970. Eleven million acres were recommended for further study.

Environmental groups had recommended 36 million acres for wilderness and 16 million for commercial use. "The Forest Service has excluded some of the best wilderness areas from protection -- often leaving only ice and rocks to be proposed for wilderness," said John McComb of the Sierra Club.

Tim Mahoney of the Wilderness Society said the administration "padded" its wilderness proposal by including 5.6 million acres of land in Alaska that had been recommended to Congress last February. He called yesterday's action "a yery timid step."

National Forest Products Association representative John Hall said the proposal would reduce the allowable timber cut on national forests by 4 percent. "But even 4 percent is in the wrong direction," he said. "We ought to be doubling the timber supply."

Hall said timber companies are worried that harvesting in the 36 million acres slated for development will be delayed by environmental lawsuits or administrative foot-dragging. If that happened, he added, "it would precipitate a crisis situation which would require congressional action."

The 62 million acres of roadless land reviewed by the Forest Service included vast tracts in the Rocky Mountains' Overthrust Bell, one of the hottest areas in the country for oil and gas exploration. While most of the promising tracts were excluded from wilderness proposals, several were designated in Wyoming, Utah, Colorado and Idaho, according to the Rocky Mountain Oil and Gas Association.

"Companies have spent millions of dollars in seismic work," said association official Paul Driessen, "and now they won't be able to drill." The gros Ventre wilderness area, a 400,000-acre Wyoming tract, is estimated to have 87 million barrels of oil and 434 billion cubic feet of natural gas, he said.

Assistant Agriculture Secretary Rupert Cutler said a special effort was made to propose wilderness areas in eastern forests near large cities. The recommendations include 16 tracts cov ering 133,000 acres in Virginia and West Virginia.

Wilderness designation was also proposed for 66,478 acres in North Carolina; 3,887 in Tennessee, 39,670 in Georgia and 24,675 in Florida.

Environmentalists were outraged, however, that of the 55,720 acres under study for wilderness in Vermont, none were proposed. Cutler said town selectmen told the Forest Service they would block any private land purchases for national forests if any wilderness was recommended.

Controversy is also likely over proposals for wilderness aneas in the Great Plains states of Narth Dakota, Nebraska and Colorado which environmentalists say were "token efforts."

The federal wilderness designation means that no timbering, roads or mechanized vehicles are allowed, raising the hackles of people who like to drive into scenic areas rather than canoe or backpack. Hardrock mining and oil and gas exploration are severely restricted.