Federal agencies that face the prospect of demoting anywhere from 10 per cent to 30 per cent of their work forces now may ask for authority to freeze those demotion actions for extended periods of time.

The Civil Service Commission now is ready to listen to and approve agency plans for deferring large-scale demotions, if the agencies can prove that such actions would have an adverse impact on their missions, and would promise to straighten out misclassification problems.

Although nobody knows the extent of overgrading (or undergrading) in government, studies by agencies and the Congress have shown that in some offices, as many as three of every 10 workers are in jobs that are over-has cracked down on overgrading in recent years. The result has been more and more pressure to rectify errors that had been allowed to stand for years.

CSC has been taking a hard line with agencies that came to it for permission to delay downgradings. It did give the Department of Health, Education and Welfare permission to hold off on the downgradings, but only because HEW's problems was so bad, and it was undergoing a reorganization. In return for the two-year demotion freeze HEW had to agree to very tough conditions to clean up its personnel operation, and get its grades in order.

Other agencies had asked CSC to make the demotion deferral government-wide, but CSC refused to do so. It is still balking at the idea of a government-wide moratorium on demotions - pending legislation in COngress that would freeze demotions - but it now is prepared to listen to individual agency appeals.

If they can make a case as good as HEW's, officials say, they will be allowed to hold off on major demotion actions pending legislation that would "grandfather" in employees who have been victims of "no fault" demotions since last Jan. 1.