Comptroller General Elmer B. Staats has told the Carter administration that it cannot legally phase out the controversial Clinch River breeder reactor and that any government official who approves spending to terminate the project will held personally liable for the debt.

Staats, head of the congressional General Accounting Office, warned the administration Friday afternoon in hand-delivered letters of his intention "to disallow expenditures that do not accord with opinions" of GAO that the administration has no choice under law but to build the $2 billion Tennessee project.

The project can be phased out only if Congress amends the law authorizing it, he said. Congress has repeatedly rejected Carter administration efforts to stop contruction of the reactor.

Staat's action was triggered by President Carter's signing into law last Tuesday a supplemental appropriations bill that contained $80 million for Clinch River, a demonstration nuclear reactor that, in producing electricity, makes more plutonium than it uses.

In a White House press release on the signing, Carter reiterated his position that the Clinch River reactor is a waste of taxpayers' money and that an unspecified portion of the $80 million would be used to "terminate further" the project "in an orderly way."

Staats is empowered to asses personal liability for misuse of public funds. The last time he threatened to use this power was in 1974 to secure an end to Secret Service protection for former Vice President Agnew four months after he left office.

In the Clinch River situation, a GAO attorney explained yesterday, and special, such as Energy Secretary James E. Schlesinger or a subordinate, who "certifies a voucher" to pay for termisation of the project would automatually be deemed by Staats to be in debt to the government for the fends involved. This could amount to millions of dollars, according to Ralph Lothis, senior attorney in the GAO general counsel's office.

"The statue allows us to set them up in debt to the government,Lotkin said, "Staats has sole authority to do it."

Last April Carter attacked the Clinch Riyer project and said he would ask Congress to eliminate the funding. During his campaign for the White House in 1976 he said he would develop a policy to control the spread of plutonium, which is used to manufacture nuclear weapons. Pro-nuclear energy groups want to move atomic power plants away from using uranium and into plutonium, and Clinch River is supposed to demonstrate the feasibility of doing this. It would use reprocessed plutonium as a fuel and "breed" additional plutonium that in turn could be used as a fuel.

But Congress has supported the Clinch River reactor construction porject and has had the GAO's legal opinion as a weapon. In opinions in June and December last year, Staats held that the law authorizing Clinch River said moneys could be spent only for "the design, development, construction and operation" and that "they may not be used to terminate such activities."

Using any part of the $80 million in the supplemental appropriations bill "to terminate further" fast breeder reactor construction "would not be in his letter Friday. Further, he quoted a portion of the United States Code that says "the officer or employe certifying a voucher shall . . . be held accountable for and required to make good to the United States the amount of any . . . payment prohibited by law . . . ."

"If we find payments made in disregard of our opinion on the scope and operation" of the Clinch River authorization, Staats said, "you are further informed that, in light of this advance notification provided, relief from liability of the certifying officers involved will not be granted. . . . "

So far Congress has appropriated $505 million for the project. The fast breeder reactor is supposed to be operational in the mid-1980s. CAPTION: Picture, ELMER B. STAATS . . . keeps $2 billion project alive