Five major environmental groups urged President Carter yesterday not to allow himself to be caught in the "synfuel panic" as he prepares his new approaches to energy problems.

At a news conference and in a letter carried last night to Camp David, the five groups called on the president to stress lower-cost conservation programs and avoid a massive commitment to synthetic fuels.

They complained that Department of Energy options presented to Carter during the past week have been "deficient" in conservation approaches and have ignored creative ideas in the private sector."t"Is is a tragic error," said Jonathan Lash of the Natural Resources Defense Council.

The other protesting groups were Friends of the Earth, the Sierra Club, the Environmental Policy Center and the Wilderness Society.

Spokesmen for the groups said at the news of conference that there has been an "encouraging shift" of sentiment in Congress in recent days, raising questions about the economics and environmental hazards of large-scale synthetic fuel development schemes.

"In the last week, people have been saying 'we have to take a closer look' but for the previous month and a half, synthetic fuel was this year's version of 'The Big Rock Candy Mountain'," said David Masselli of FOE.

In their letter to Carter, the environmentalists said, "we cannot comprehend why your advisers did not examine the full range of conservation possibilities in light of today's higher energy prices and the vast sums we are now proposing to spend for new supply and production."

"The simple test should be how we can buy the most BTUs [a measure of heat] for the dollar . . . This test appears never to have been applied," their letter said.

They urged Carter to tell the public the "real facts" about synfuels - that each plant could cost $5 billion or more, using untested technology to produce $40-per-barrel oil; that synfuels will not end gasoline lines for at least a decade, and that they produce "unacceptable" environmental risks.

They said the president's energy strategy, part of which he is expected to announce Sunday evening, should emphasize conservation measures, more solar development, broader research on less-ostly synfuel programs and more oil and gas exploration.

"Legislators and policymakers have seized on synfuels as an easy, popular way to avoid facing the hard choices our energy situation demands," their letter said. "Instead of spending tens of billions of dollars only on an untried technology, you . . . should be looking for cost-effective energy investments which can produce more energy at a lower cost."

Gary De Loss of EPC said that federal investment in conservation programs could produce almost immediate energy-saving results, while stimulating employment and protecting the environment.

"Conservation investments are far better pork-barrel than synthetic fules," De Loss said. "Conservation programs will mean spending in every congressional district - all areas will benefit." CAPTION: Chart, Daily Gasoline Guide