The Pentagon has drafted a directive authorizing a vast expansion of the use of lie detector tests for government employes.

Polygraph examinations could be used for everything from screening job applicants to tracking down leaks to the press under the draft directive obtained by The Washington Post and confirmed by the Pentagon yesterday as being under review.

A top Defense Department official acknowledged that lie detector tests could be used more widely if the draft is adopted than under a 1975 directive now in force, but he stressed that government employes still would have the right to refuse to take them.

Hundreds of Pentagon employes in particularly sensitive jobs, however, are being asked to sign forms waiving their right to refuse to take lie detector tests, said the official, who asked not to be identified.

The 1975 directive emphasizes that the polygraph should be used sparingly, ordering Pentagon executives to "preclude its use in cases other than serious criminal cases, national security investigations and highly sensitive national security access cases . . . ."

Pentagon officials described the draft directive as "an update" which would provide "additional insurance" against serious security breaches. Critics, including some active duty military officers and Pentagon civilians, contended that the Reagan administration was trying to intimidate Pentagon employes.

Critics argued that the draft directive would not only institutionalize the use of lie detector tests at the Pentagon, but also spread their use in other government departments that do not deal primarily in military or intelligence information. Pentagon officials would be authorized by the draft directive "to provide polygraph services to entities other than Department of Defense components" so long as they followed certain rules for administering the lie detector tests.

Defense Secretary Caspar W. Weinberger, asked how and why he wanted to expand the use of lie detector tests, refused to discuss the matter, saying the directive was still in preliminary stages of promulgation "and we'll let it go at that."

The draft directive already has been submitted to the Office of Personnel Management to determine whether it conforms to civil service rules. The agency has suggested some changes, including going further to inform people of their right to refuse a polygraph examination and to hire a lawyer before answering questions.

The Pentagon's general counsel, William H. Taft IV, said last night he was not certain when the draft directive will be in final form, but added that he intends to have it published in the Federal Register for comment.

Although lie detector tests are routinely administered to Central Intelligence Agency employes, they have never been institutionalized to the same extent at the Pentagon, which has 3 million people on its full-time payroll, 2.1 million in uniform and 947,000 civilians.

Deputy Secretary of Defense Frank C. Carlucci, a former deputy director of the CIA, is a strong believer in the use of polygraphs. He ordered lie detector tests for Pentagon officials last January in an unsuccessful attempt to find who disclosed to The Washington Post information about Pentagon cost estimates of President Reagan's arms buildup.

John Shattuck, executive director of the American Civil Liberties Union, said after reading The Post's copy of the draft directive on use of the polygraph that it was "the broadest I have ever seen.

"If used in the unlimited fashion the directive appears to permit," said Shattuck, "it would allow an enormous invasion of the right of privacy of Defense Department employes, contractors and even personnel in other government departments."

Here are major differences between the 1975 directive now in force and the draft directive:

* Screening employes. The current directive forbids using polygraphs "as a screening or selection device, as a condition of employment or as a routine part of personnel security investigations of such persons." Exceptions are made for military personnel assigned to the CIA and National Security Agency.

The draft directive would "require" polygraph examinations for military, Defense Department and General Services Administration personnel "to assist in determining their eligibility for initial or continued employment, assignment, or detail for duty" at the CIA, National Security Agency and Defense Intelligence Agency.

Giving lie detector tests to employes of privately owned defense firms also would be a significant departure from present practice, according to a Pentagon official who is reviewing the draft directive.

* Aiding investigations. The current directive states that "the polygraph shall be employed only as an aid to support other investigative techniques and be utilized generally only after the investigation by other means has been as thorough as circumstances permit."

The draft directive repeats that polygraphs should not be regarded "as conclusive in themselves" but appears far less restrictive in stating when they can be administered.

Polygraph examinations could be given, for example, "to investigate an alleged unauthorized disclosure of classified information or alleged acts of espionage, sabotage, treason, subversion, sedition or terrorism."

Shattuck contended this provision would enable "a government executive to throw polygraphs at his employes on the basis of just an allegation that something in a newspaper was a security leak, without knowing it really was or not."

* Refusal rights. The existing directive orders Pentagon executives to "ensure that it [a polygraph] is used only when the individual taking the polygraph examination volunteers to take the examination."

The draft directive suggests that a person who refuses to take a polygraph will be regarded with added suspicion, stating: "Adverse action shall not be taken against a person solely for refusal to take a polygraph examination."

* Overseer. Under the current directive, the Pentagon's controller, traditionally a civilian, oversees polygraph policy. The draft directive would give this responsibility to the deputy undersecretary of defense for policy, currently retired Army Gen. Richard G. Stilwell whose office wrote the new directive.

Shattuck took particular exception to the proposal in the draft to allow polygraphs to be used "to resolve credible derogatory information developed in connection with a personnel security investigation of a Department of Defense civilian, military or contractor personnel that cannot be resolved in any other manner."

"Did the employe cheat on his wife? They could use the polygraph to delve into that any time they wanted to under that language," he said. "Any time they got dirt on anybody, they could wire somebody up."

The ACLU lawyer, who represented former Pentagon and National Security Council employe Morton Halperin in his wiretapping suit against former secretary of state Henry Kissinger, said proposed procedures also invite the government to go to the edge of technology in employing "Big Brother" tactics.

His basis for saying this is the following section in a Pentagon document outlining procedure to be followed in carrying out the polygraph directive:

"Prior to administering a polygraph examination, the polygraph examiner shall interview the individual to be examined. During this interview, the examinee shall, as a minimum, be told if the polygraph examination area contains a two-way mirror, camera or other device through which the examinee can be observed, and if other devices such as those used in conversation monitoring or recording will be used simultaneously with the polygraph."

Transcending all these objections, Shattuck said, is the way expanded use of polygraphs would help legitimize a form of examination that has proved to be unreliable, invades a person's privacy and forces him to incriminate himself in violation of the Fifth Amendment.