The federal government has been trying to persuade pregnant and breast-feeding women to limit their intake of fish because of mercury contamination. Now some federal scientists are arguing that these women should actually increase their fish consumption. The behind-the-scenes disagreement is fierce and raises serious questions for consumers.

The current official advice from the Food and Drug Administration and the Environmental Protection Agency is that pregnant and nursing women and young children can safely eat up to 12 ounces  roughly two servings  of most fish a week, but should limit their intake of albacore tuna to 6 ounces a week and avoid entirely four species of fish containing high levels of mercury.

Now the two agencies are at loggerheads over the two-serving limit. The F.D.A. has circulated a draft report suggesting that the vast majority of fetuses and infants would actually benefit if their mothers ate more than two servings of fish a week because fish contain highly beneficial nutrients that aid in brain development. The F.D.A.’s scientists argue that those benefits outweigh any potential harm.

Those contentions are sharply disputed by specialists at the E.P.A. who charged that the report had “serious scientific flaws,” relied on questionable models and should not be used as a basis for decision-making. That is a strong indictment that must be answered before the public can place any confidence in the F.D.A.’s judgment.