WASHINGTON – The top Food and Drug Administration official in charge of women’s health issues resigned yesterday in protest against the agency’s decision last week to further delay a final ruling on the whether the emergency contraceptive “morning-after pill” should be made more easily accessible.

Susan Wood, assistant FDA commissioner for women’s health and director of the Office of Women’s Health, said she was leaving her position after five years because Commissioner Lester Crawford’s decision Friday amounted to unwarranted interference in agency decision-making.

“I can no longer serve as staff when scientific and clinical evidence, fully evaluated and recommended for approval by the professional staff here, has been overruled,” she wrote in an email to her staff and FDA colleagues.

She said that Mr. Crawford’s position – that unresolved regulatory issues made it impossible to approve expanded use of the drug – is “contrary to my core commitment to improving and advancing women’s health.”

When the FDA rejected the first application last year to make the emergency contraceptive Plan B available without a prescription, officials acknowledged that the science staff had overwhelmingly favored the application. When Mr. Crawford announced additional delays Friday with a second application, he again acknowledged that the staff and managers of the Center for Drug Evaluation and Research had concluded that the drug was safe for over-the-counter use for women over 17.

Mr. Crawford said, however, that the agency was wrestling with unresolved regulatory issues regarding whether it could properly allow a drug to be sold as an over-the-counter medication for most women, and by prescription-only for girls under 17. He said the issue had to be addressed through a formal rule-making process, which can be time-consuming.

Many supporters of the Plan B application – including Senators Clinton, a Democrat of New York, and Murray, a Democrat of Washington – accused Mr. Crawford of making a political decision that ignored science and public health.

The Plan B issue has become an emotional one for advocates – who believe it will reduce the number of unwanted pregnancies and abortions – and opponents who believe that it will encourage teenage promiscuity and that in some cases its mode of action constitutes abortion. Social and religious conservatives flooded the White House with phone calls in the days before Mr. Crawford’s decision.

The FDA and mainstream medical associations consider that Plan B, which is generally effective in preventing pregnancy if taken with 72 hours of a contraceptive failure or unprotected sex, prevents a pregnancy rather than ending one. Religious conservatives and some members of Congress disagree and say that pregnancy begins with the fertilizing of the egg. They argue that anything that harms the egg amounts to abortion. While Plan B generally works by preventing fertilization, in some cases it can keep a fertilized egg from implanting in the uterus.

Ms. Wood has been the senior official for women’s affairs since 2000, and the mission of her office is to “be a champion for women’s health, both inside and outside the agency.”

Before coming to the FDA, Ms. Wood was the director for policy and program development at the Department of Health and Human Services’s Office on Women’s Health.