A significant revision of the nation's food safety laws, including elimination of the automatic ban on any substance found to cause cancer in man or animals, will be recommended to Congress today by a National Academy of Sciences panel.

A minority of the panel opposes most of the changes as giving federal administrators too much discretion in determining what to ban, saying this could endanger the public's health.

The report, to be made public today, is sure to start a new fight over the nation's food supply and the role of saccharin, nitrites and hundreds of other cnemical additives in causing cancer and other diseases.

The Food and Drug Administration has named an internal committee to draft new food safety legislation along many of the lines of the new report, it was also learned yesterday.

Congress ordered the report in 1977 when it voted to delay an FDA ban on most uses of saccharin.

Whereas the 1958 Delaney amendment would require a ban on saccharin and nitrites -- the two food additives that have caused the most controversy lately -- both could remain on the market under the provisions of the new report.

The majority of the academy group would allow the FDA to decide whether saccharin is a severe or modest risk, depending on how the agency now views the evidence that shows the low-calorie sweetener can cause animal cancers and that suggests it has caused human bladder cancers.

The FDA then could either ban the sweetener "in whole or in part," or place a warning label on foods and drinks containing it.

The panel's recommendation on saccharin is only one part, however, of the sweeping way in which the government's approach to food safety would be changed.

Current food laws often give federal regulatory agencies little discretion when even traces of dangerous substances are found. And modern chemical methods are able to find traces that were undetectable when the food laws were written.

The Delaney amendment -- named for its author, Rep. James J. Delaney (D-N.Y.), who is now retired -- bars any substance causing any cancer in man or animal.

But a Congress largely shocked by the proposed saccharin ban asked the scientific body to consider the safety of such substances from a standpoint of potential benefits as well as risks.

The panel will reply that weighing risks against benefits is largely a public policy decision, not the kind of factual finding scientists can supply.

Instead, panel members reported yesterday, the panel will recommend "a new statutory basis of regulation," under which suspect foods and additives would be classified by the FDA -- often with Agriculture Department advice -- as "high," "moderate" or "low" risk.

In each case, says the panel, the FDA should then have "regulatory discretion," since "safety cannot be defined entirely by scientific processes."

The majority of the panel, including the chairman, Dr. Frederick Robbins of Case Western Reserve University in Cleveland, agreed that this system -- treating all foods, including possibly cancer-causing substances, "uniformly" -- would help end "the irrelevant and impractical" rules that now "confuse and impede rational scientific decisions."

Substantial minorities of the 14-member group say:

It is impossible for the FDA to assign risk categories, since "the ability of science to quantify human risk" safely is still primitive.

Federal officials should be given little discretion in applying safety rules; otherwise, the strongest interests may succeed in allowing unsafe foods to menace everyone.

Saccharin, if left on the market, may cause many cancer in the future in youngsters who now drink several drinks.