This week, for the 30th time in 23 years, the Food and Drug Administration is expected to postpone a decision on whether to ban six widely used food and drug dyes, four of which have been shown to cause cancer in laboratory animals.

The agency was supposed to decide either to ban or approve the dyes by June 6, the deadline set after previous delays. The additives will continue to be used in consumer products pending the FDA's decision.

The agency's staff has recommended banning four of these color additives several times during recent years. Three FDA commissioners have also recommended banning the additives, but the Department of Health and Human Services did not act on these recommendations.

One dye, Yellow No. 6, is used in some beverages, desserts and candy. The other five, Orange No. 17, and Red Nos. 8, 9, 19, and 37, are used in drugs and cosmetics.

Postponing the decision will permit further scientific review of the dyes, said agency spokesman James Greene. But consumer advocates and some members of Congress believe the postponement is a result of pressure from industry, not a need for further review.

"The agency is just trying to figure out how they can rationalize the fact that they're breaking the law by allowing cancer-causing dyes in food, drugs and cosmetics," said Dr. Sidney Wolfe, director of the Washington-based Health Research Group, one of two consumer groups that has sued FDA over the delayed decision. The suit is expected to go to trial this year. Although unwilling to approve the additives, the FDA says the dyes pose no threat. "The continued provisional use of these additives presents no hazard to the public health," said Greene.

The debate about the additives revolves around whether a safe level of known carcinogens can be established. Industry officials and some scientists claim the dyes could cause cancer only if consumed in large quantities. Other scientists maintain there is no safe level for known carcinogens.

Under law, the FDA was supposed to evaluate the safety of all food, drug and cosmetic dyes by January 1963. Last year, a congressional report criticized the agency and HHS for postponing a decision on 10 color additives, including these six. Since then, the FDA approved one additive (Yellow No. 5) and defered a decision on three (Red Nos. 3, 33 and 36). Greene said action on the remaining six dyes will be delayed for a few months or a year.

The delay drew sharp criticism from Rep. Ted Weiss (D-N.Y.), chairman of the House Government Operations subcommittee on intergovernmental relations and human resources, which prepared last year's report.

"This is an ongoing embarrassment to the whole regulatory process and system of law -- it's shameful and indecent," said Weiss. "The agency has placed the commercial concerns of the affected industries above the concern for the health and welfare of the American public."