Secretary of Health, Education and Welfare Joseph A. Califano Jr. yesterday proposed new federal regulations to ban age discrimination in all federal and federally aided benefit programs.

The new regulations could force medical, dental and law schools to accept applicants who had reached age 50, 60 or older, if otherwise qualified, officials said. However, the regulations won't become final for at least six months and then must be supplemented by further detailed rules.

The regulations will implement the Age Discrimination Act of 1975.

The 1975 law barred discrimination based on age in all federal benefit programs and in nonfederal programs receiving federal financial assistance, although distinctions are allowed when a program is aimed at a specific age group. The 1975 statute does not involve hiring practices, which are already covered by a separate 1967 law.

Califano, in a speech to conference sponsored by National Journal, said: "Today we begin a new journey on the road to equal opportunity... at the dawn of a four-generation society."

The regulations spelled out programs where age distinctions may be permitted by existing provisions of law, or would be allowed if justified.

The document said that the new regulations will not interfere with compulsory school attendance laws based on age, receipt of old-age benefits like welfare and Social Security, feeding programs aimed at the young or old, reduced bus fares for students and aged, sports programs dividing children into age groups, or Head Start participation for young children.

But the document said, "A... difficult example is that of a medical school which does not accept applicants over a certain age because of the high cost of medical education and the more limited period of active medical service that can be expected from an older medical school graduate. This age limitation, however, would appear to violate the Act... Denial of research awards to persons over age 70 would likewise appear to be prohibited."

A Califano aide said the medical school language of the document also applied to other professional and graduate schools and colleges. If the regulations become final, noncomplying institutions would lose federal aid.

Califano said the proposal will unleash a great national search for all aspects of unfair and invidious age distinctions in government programs "to identify and then eliminate them."

Yesterday's proposals are intended as guidelines for all agencies. When they are put into final form in about six months, after public hearings and changes, each federal agency will then begin drafting detailed regulations for its own programs based on yesterday's guidelines.

One unusual proposal in the regulations is as follows: "We propose... for the first time in the history of civil rights enforcement, to enlist the federal Mediation and Conciliation Service to review claims of [age] discrimination and resolve them promptly, within no more than 60 to 90 days."