The Labor Department issued regulations Friday barring most private employers from using polygraph or lie detector tests to screen job applicants and greatly restricting use of the devices to test present employees.

The regulations, which take effect Dec. 27, implement legislation passed by Congress and signed by President Reagan last June outlawing about 85 percent of the current use of polygraph examinations and voice stress analyzers.The congressional Office of Technology Assessment had estimated that 2 million polygraph examinations were conducted last year - 90 percent by private employers.

Under the new regulations, some 7.2 million employers nationwide will be required to put up posters next month summarizing the prohibitions and exemptions and outlining the rights of any worker asked to take a lie detector test.

Fred Alvarez, assistant labor secretary for employment standards, said the posters will be mailed out in three or four weeks.

Employers who keep requiring that job applicants or current employees take the tests - except for the allowed exemptions - or do not abide by other safeguards in the regulations can be fined up to $10,000 for each violation.

The regulations also give anyone required to take the test in violation of the new law the right to sue employers in federal and state courts for relief, such as employment reinstatement, promotion and any payment of lost wages and benefits.

Exempted from protection under the ban are employees of federal, state and local governments or federal contractors engaged in national security, intelligence or top secret activities.