A Pentagon commission studying ways to prevent espionage has recommended that Congress give the Defense Department increased power to conduct random lie detector tests to help ferret out potential spies in the military and among defense contractors, the panel's chairman said yesterday.

The report by the commission, headed by retired Army general Richard G. Stillwell and appointed by Defense Secretary Caspar W. Weinberger after revelations about the Walker family spy ring, is to be released today.

The Pentagon currently has authorization to conduct 3,500 "counterintelligence" polygraphs this fiscal year among Defense Department personnel and civilian employes cleared to see "top secret" information or higher.

However, that power is subject to annual review by Congress. The commission report recommends that the lie detector authority be "institutionalized" so that the Pentagon can better plan how many polygraph examiners it needs to train, Stillwell said. Congressional oversight of the program would be maintained, he added.

The report also recommends "more vigorous command and supervisory authority in ensuring that the security policies are indeed observed and enforced throughout the Department of Defense," he said.

It suggests, among other things, instilling a "heightened awareness of the reality of the threat" of espionage through training and briefing programs for those with access to classified information, he said.

In addition, Stillwell said, it recommends stringent enforcement of the rule that only those with a "need to know" see a particular classified document.

"A clearance at every level is not an 'open sesame' to everything in that level," Stillwell said.

The recommendation for increased polygraph authority -- the only legislative change called for in the report -- is sure to be controversial on Capitol Hill, where copies of the report were distributed yesterday.

In June, the House voted overwhelmingly to give the Pentagon broad power to subject to lie detector tests the 4.3 million military and civilian employes with access to classified information. That power was scaled back to the current 3,500 by a House-Senate conference committee.

Stillwell said he did not see the polygraph proposal as the "main thrust" of the commission recommendations.