"It's important for the public to recognize the nutritional value of fish, and it's important that we work hard to keep the food supply as low in contaminants as we can," Mahaffey said.
Environmental and public health groups said the report should serve as a wake-up call to the Bush administration.
"This heightens the urgency for FDA to give women adequate advice on what fish are safe to eat, and it ups the burden on the administration to cut mercury pollution from coal-fired power plants," said Jane Houlihan, vice president of the Environmental Working Group, a research and advocacy organization.
"The problem is twice as serious as previously believed."
Houlihan said the FDA should particularly warn women not to eat albacore, or white meat tuna, which is high in mercury but is not on the FDA's list of fish to avoid.
Last week, the EPA announced its plan to reduce mercury emissions from power plants by 70% over 15 years.
The agency's own Children's Health Protection Advisory Committee called the proposal inadequate.
