The nation's third-largest insurance company has told leaders of 25 energy-rich Indian tribes that it is prepared to make significant investments in Indian-owned energy ventures.

The proposal could create a new energy equation in the West, freeing the Indian tribes from their near-total dependance on the giant oil companies that now have a hammerlock on tribal development.

The offer by Carleton Burtt, executive vice president of the Equitable Life Insurance Society, was hailed by tribal leaders who once talked of obtaining assistance from Arab-oil producing nations as a welcome step toward energy independence.

"Equitable's interest is enlightened self-interest," Burtt told a two-day meeting of the Council of Energy-Related Tribes that concluded here yesterday. "We look for opportunity to invest large amounts of capital in development."

LaDonna Harris, president of Americans for Indian Opportunity, said that the Equitable proposal, which she credited to company chief executive Coy Eklund, was the forerunner of others that will be made by seven major insurance companies.

"Two years ago this couldn't have happened, but there is a genuine interest now," Harris said. "They will follow Equitable's lead, and it's now up to the tribes to come forward with programs for them to invest in."

The western Indian tribes belonging to the Council of Energy Related Tribes own 50 percent of the nation's uranium, a third of the low-sulfur strip able coal and substantial oil, gas and geothermal reserves.

The Navajo tribe is by far the largest with two-thirds of the population of the energy-owning tribes and more than a third of the reservation acreage.

Because of Navajo dominance and the personal prestige of Peter McDonald, chairman both of the council and of the Navajo nation, the tribe generally is considered to be first among equals by the western Indian leaders.

McDonald, fresh from a decisive reelection victory to his third four year term as Navajo Council president, lauded Burtt's offer and also predicted that it will be the forerunning of similar proposals.

But MacDonald cautioned that Indians will scrutinize every proposal carefully and are "not prepared to compromise with someone just because he treats us nice, buys lunch for us and says the right things."

In discussing the energy development on Indian lands following Burtt's speech, MacDonald made these points:

The Indians should appraise their own resources, using money put up by the federal government, but hiring their own geologists and appraisers.

Simultaneously, it is important for Indians to become geologists, chemists, hydraulogists and other specialists. For this purpose, MacDonald said, the economic assistance of the big oil corporation is welcome.

Indian tribes should strive to develop their own resources, either independently of as a joint effort with venture capital.

It is such venture capital efforts that Burtt appeared to have in mind when he addressed the Indian Council.He told reporters after the meeting that his company would be interested in providing "equity ownership with proper security and an economic rate of return." In his speech Burtt quoted Equitable President Eklund as saying that corporations would have to become socially responsible to survive in the world where people are increasingly skeptical of corporate motives.

Though Burtt was warmly applauded, deep doubts remained among the Indians about both the corporate giants and the U.S. government. The skepticism is a reflection of generations of past experience.

One document circulated here by representatives of the Jicarilla Apache Tribe in New Mexico spelled out what representatives of nearly all the tribes have been saying - that they were cheated out of royalties in leases that were casually or illegally awarded to oil companies by the federal government.

A lawsuit by the Jicarilla Tribe against Secretary of Interior Cecil Andrus and 23 oil companies and their affiliates contends that leases on 276,000 acres of tribal land - 37 percent of the Jicarilla reservation's total acreage - should be declared invalid because they violate various legal requirements including the necessity for an environmental impact statement.

The leases, among the largest on any Indian reservation, were made during the Nixon administration. The tribe received $685,000 in bonus money for leases that Indians calculate would be worth at least $80 million if fair market value had been paid.

According to a document accompanying the lawsuit, the Interior Department's Bureau of Indian Affairs did not bother to check past evaluations made by oil companies already on file with the federal government when the lenses were made. These showed that the land was worth far more than the oil companies were paying for the leases, the Indians contend.

MacDonald also was critical of the federal government's apparent unwillingness to commit money to Indian development programs despite countless studies.

"Interior recites statistics to us about our plight that we already know too well," MacDonald said. "But when it comes to doing something about it, they he-haw around, contract with Harvard and write forwards to books."

Nonetheless, the federal government is, for the first time, funding the Council of Energy-Related Tribes in a serious way. Formed in 1975 without funding, the council had a $200,000 budget a year ago. Now it has a $3 million budget and yesterday celebrated the opening of its Denver office.