SANTA BARBARA — A senior official of the U.S. Interior Department, in a wide-ranging critique of the Endangered Species Act, said Thursday that the needs of an expanding population, agriculture interests and burgeoning development in the West should be given equal consideration with endangered plants and animals.

Attending an endangered species conference in Santa Barbara, Assistant Secretary of Interior Craig Manson criticized the critical-habitat provision of the law, which limits development in areas favored by threatened species, saying such designations aren't necessary for the perpetuation of many plants and animals.

Manson oversees the U.S. Fish and Wildlife Service, the agency responsible for enforcing the Endangered Species Act.

In an interview before his speech here, Manson said the 30-year-old environmental law is "broken" and should no longer be used to give endangered plants and animals priority over human needs.

"The problem is the act was not written with a great deal of flexibility," he said, adding that the interests of developers and private property owners in some cases should prevail over endangered species.

"There are so many things we did not anticipate 30 years ago. It was almost written in a public policy vacuum, without any consideration of the potential impacts of the act on larger and different issues. We didn't anticipate the potential conflicts. We have to recognize that, A, we can't protect everything, and, B, we have to carefully examine whether we should try to protect everything, and at what cost?"

But former Interior Secretary Bruce Babbitt, who also was a speaker Thursday, was sharply critical of the Bush administration's stewardship of endangered and threatened species.

"There is nothing wrong with the Endangered Species Act. It works," said Babbitt, who served during the Clinton administration. "The problem is this administration is not enforcing it and it doesn't want it to work. They want it to fail."

Babbitt said the act can be highly flexible, citing a compromise involving the San Francisco Bay delta. There, state and federal officials came up with a plan for diverting water to San Joaquin Valley farmers and Southern California city dwellers that left enough to sustain native fish in the delta. Babbitt said the agreement is a model of how the act can foster positive change.

But Babbitt agreed with Manson on critical habitat, saying the statute could be struck down today with "no real-world consequences," noting that habitat provisions lie elsewhere in the act.

The Bush administration has placed fewer plants and animals on the endangered species list than any other in the act's 30-year history. Bush has listed 20 species since taking office. President Clinton listed 211 during his first three years in office.

Conservationists note that none of the listings made during Bush's tenure were done voluntarily by the Fish and Wildlife Service. All came as a result of lawsuits or petitions from private groups.

This week, the Senate passed a bill that would exempt military bases from some sections of the act, including the critical-habitat provision. Manson said he supports the bill.

Manson, a former California Superior Court judge, served six years as general counsel for the California Department of Fish and Game.

In a recent interview with The Times, Manson questioned the wisdom of extreme efforts to stave off extinction of all species. "If we decide we are going to spend $100 million to save a species we've imperiled, why are we doing that? Are we doing that because it serves human interests to do that? Are we doing that for the exercise of saving something that nature can't take care of … regardless of our efforts? If we are saying that the loss of species in and of itself is inherently bad — I don't think we know enough about how the world works to say that."

The act's purpose, he said, "is not to create a perpetual hospice for threatened or endanged species. It's our responsibility to get them to the point of recovery."

Conservation groups are highly critical of Manson's stance toward critical habitat, citing the Fish and Wildlife Service's own statistics that show endangered species with critical habitat designation are twice as likely to be improving as species without.

"The reason groups like mine pursue protection with critical habitat is that the science is absolutely clear that species with critical habitat are doing better," said Kieran Suckling, executive director of the Center for Biological Diversity.