The federal government says not to worry about Special Form 189, the pledge that federal workers have to sign saying they won't give away secret information. Nobody will get hurt for not signing it, and nobody will be punished for blowing the whistle on corruption and incompetence, the feds promise.

Tell it to George Schoenberg.

Schoenberg used to be a cost analyst in the Army's Tank-Automotive Command in Warren, Mich. He earned several awards for spotting costly errors in defense contracts. But apparently there is a fine line between making constructive suggestions and making your bosses nervous. Schoenberg's repeated criticism of management shortcomings got him fired last year. He also lost his security clearance because he refused to sign Form 189. Through arbitration, Schoenberg was rehired last August, but without the back pay he lost during nine months of unemployment and without his ''secret'' security clearance.

With no clearance, Schoenberg's job options were limited. He was finally made a program analyst. A two-finger typist, he spent his time hunting and pecking data into a computer. Army personnel official Anita Carman told our reporter Tanya Isch that Schoenberg has finally had his security clearance reinstated and he will get another job.

Schoenberg's nightmare with Form 189 is an example of the possibility for abuse that should be giving us all bad dreams and one of the reasons Congress, at the end of the session just concluded, ordered an end to the use of it. An amendment to the fiscal 1988 spending bill signed by President Reagan last Tuesday forbids the government to spend any money implementing or enforcing Form 189.

On the surface, Form 189 sounds like a good way to keep federal employees from giving away state secrets. Deep down, it is a threat to the way ordinary people keep their government in check -- ordinary people like you, the press and even members of Congress.

We agree with Rep. Gerry Sikorski (D-Minn.), who said, ''The term 'national security interests' has always been the last refuge of administrations more concerned with hiding their problems than with protecting the public interest.''

Members of Congress have been particularly incensed about being asked to sign Form 189 to gain access to documents and people in the agencies they are supposed to oversee.

To appease Congress, the Reagan administration declared a moratorium on the practice of suspending security clearances of employees who won't sign. A lost security clearance often means a lost job.

The White House also tried to assure employees and critics that Form 189 won't put the lid on whistle-blowers. There are laws to protect employees who report fraud and waste, and the executive order that created Form 189 in 1983 forbids the classification of documents merely to hide waste, errors and illegalities.

The soothing reassurances apparently weren't enough to mollify Congress, which is no surprise considering the way the feds have misused Form 189.

The Air Force, for instance, originally deemed that reluctance to sign Form 189 ''will be considered lack of personal commitment to protect classified information.'' The Air Force also required employees who didn't even need security clearances to sign the form; it recently modified its rules.

Under the old rules, Louis Brase lost his security clearance as a training manager for the Air Force in San Angelo, Texas, when he refused to sign this past June. The Air Force ruled that his refusal ''reflects adversely on his trustworthiness.'' Brase got his clearance back, but says he received a low job performance rating in retaliation.

Brase told a congressional subcommittee looking into Form 189, ''One reason why Ollie North and his cohorts got by with a wide range of illegal activities for almost a year was the fact that many of the persons in government who were aware of his activities were afraid to reveal his activities by the 'security' blanket put over their actions.''

In addition to the blatant misuse of Form 189, the form itself carries a word that could be the Bermuda Triangle of federal loopholes. Form 189 prohibits the disclosure by a federal employee not only of anything classified but of anything ''classifiable.'' The poor worker has to promise not to shine a light on anything that is public information today but could be secret information tomorrow at someone's whim.