Leonard Kapiloff, publisher of the Washington Jewish Week and several suburban Washington newspapers, was sued yesterday for alleged sex discrimination by a former Jewish Week staff writer who said she was paid far less than a male reporter with a similar job.

The suit by Janice L. Kaplan was filed in U.S. District Court in Washington by attorneys for the Anti-Defamation League of B'nai B'rith, a Jewish human rights organization, and by lawyers for the Women's Legal Defense Fund.

Kaplan, 27, said she had worked for the Jewish Week from late 1978 until last month, when she resigned to become a public affairs officer for the League of Women Voters.

According to the suit, Kaplan became senior staff writer in November 1983, three months after Kapiloff bought the paper. But shortly after that, the suit says, a male reporter was hired as a staff reporter at a salary of $28,995; Kaplan was earning $18,000. After she complained, the suit says, Kaplan was given a raise to $23,500, but her salary never went higher, the suit says.

The suit says Kapiloff made "disparaging remarks about women on several occasions" and called Kaplan and other female staff members "Sweet pea" and "Sweetie." It says Kapiloff told her that when hiring an editor he was "specifically looking for a man."

Yesterday an assistant to Kapiloff said he was out of town and could not be reached for comment.