Backlash from the forest fires that have devastated Yellowstone National Park in recent weeks reached the White House Thursday as angry Western Republican senators put heat on the National Park Service policy of letting naturally caused fires burn.

Sen. Jake Garn, R-Utah, blasted the "let it burn" policy adopted in 1972, saying it "has resulted in the worst forest fires in modern North American civilization."It is inconceivable to me that we would sit back and allow this kind of disaster to sweep uncontrollably through some of our most beautiful national treasures - Yellowstone National Park and several national forests throughout the West," Garn said.

The Western forest fires still burning this week were compared to the 1934 Tillamook Burn, in Oregon, and the Maine fires of 1947 that swept a 120-mile-wide swath across that state.

President Reagan, smarting from the criticism from his own party, dispatched Interior Secretary Don Hodel and Agriculture Secretary Richard Lyng to the west to deal with the fires.

Garn blamed "extreme environmentalists" for imposing the let it burn philosophy on the Park Service. "They believe that the remedy for saving a forest is to let it burn.

"Periodic small burns do have a cleansing effect which tends to keep a forest healthy," he conceded, "but I reject the theory that these fires should be allowed to burn without restraint."

He cited an editorial in an environmentalist newspaper, "High Country News," which was titled: "Save the Forests: Let Them Burn. He said, "those who espouse this philosophy must accept the responsibility for getting us into this tragic mess."

Garn said more than $160 million has been spent so far to fight Western fires this year - $60 million in Yellowstone alone. He said 30,000 firefighters from 39 states have been involved.

Garn isn't alone in his criticism.

Sen. Alan Simpson, R-Wyo., Sen. Malcolm Wallop, R-Wyo., Sen. James McClure, R-Idaho all complained to the President that Park Service Director William Penn Mott's fire policy is a disaster.