D.C. City Council member H.R. Crawford (D-Ward 7) has demanded that city officials stop a program in which teen-age mothers tell junior high school students about sexual activities because the students "are not ready" to discuss sex openly.

Crawford became upset after he heard young mothers talk at Fletcher-Johnson Education Center this week. In a letter to Joyce Ladner, chairwoman of the Mayor's Blue Ribbon Panel on Teen-Age Pregnancy Prevention, Crawford said the hearings "are more detrimental than helpful.

"I believe that such hearings contain subject matter that is too sensitive for the very young and should not be held in our junior high schools at all," Crawford wrote. "The discussions should not be permitted to digress onto subjects dealing with the youth speaking of their sexual activity in explicit terms."

Ladner, a professor of social work at Howard University who is in charge of the school visits, declined comment on the letter, which she said she had not received. One panel member called Crawford's remarks "narrow-minded."

Fletcher Johnson principal George Rutherford disagreed with Crawford and said the hearings should be held in junior high schools "because we're educating people, and that's important.

"If we are able to save four or five students from becoming pregnant in the junior high schools, then the hearings are worthwhile," Rutherford said.

D.C. School Superintendent Floretta McKenzie talked to Crawford and said his complaints "did pose some concerns for me."

McKenzie said she will contact panel members to discuss ways to prevent the hearings from becoming counterproductive. "While we want the panel members to get a firsthand look at students, we don't want the situation to be oversensationalized," McKenzie said.

At the hearing Crawford attended, several teen-age mothers warned the panel and about 300 youths of the dangers of sexual activity. One girl said she used sex to "keep my man."

At this point, Crawford said, "You have no right to have sex. You are not women and men. You are boys and girls." Crawford said that television, movies and radio stations that broadcast programs with sexual overtones are a leading cause of teen-age sexual activity.

In the letter, Crawford also charged that the panel and the press coverage of the hearings "suggested that this is strictly a black problem." Crawford said later that some hearings should be held in predominantly white private schools.

About 89 percent of black female teen-agers and 65 percent of white female teen-agers are sexually active, according to the National Center for Health Statistics. About 80 percent of all black male youths and 77 percent of white male youths are sexually active.

Barry appointed the panel last May to investigate the pregnancies among teen-agers in D.C., where one of every five new births is to a teen-ager, a rate higher than the national average, Ladner said. In D.C., 1,792 babies were born to teen-agers last year, she said.

According to the National Center for Health Statistics, 28,917 girls 15 and younger became pregnant in 1980. Among those 15 to 19, there were 1,077,992 pregnancies, of which 552,161 resulted in live births.