Seven leaders of environmental and consumer agencies during the Carter years announced plans yesterday to blow the whistle on the Reagan administration's "assault on public health and safety programs."

"We're forming the loyal opposition," said Joan Claybrook, former administrator of the National Highway Traffic Safety Administration.

She called the nation's environmental, health and safety regulations "one of the best buys the American people ever had in government," and charged that the Reagan administration has "ignored the law . . . failed to enforce the law . . . cut the flow of information . . . and caused a severe brain drain within the agencies" because of its antiregulatory policies.

Claybrook, who now works with consumer advocate Ralph Nader, is one of the seven Carter administration leaders who make up the board of participants of the new group, called the Regulatory Audit Project.

The others are Eula Bingham, former administrator of the Occupational Safety and Health Administration; Peter Bradford, former commissioner of the Nuclear Regulatory Commission; Douglas Costle, former administrator of the Environmental Protection Agency; Carol Tucker Foreman, former assistant Agriculture secretary for food and consumer services; Susan King, former chair of the Consumer Product Safety Commission; and Michael Pertschuk, former chairman and present member of the Federal Trade Commission.