The former head of intellectual property at Kasowitz, Benson, Torres & Friedman sexually harassed at least 12 female employees at the firm — including making advances on seven of them in one night — before he was fired in December, according to a lawsuit filed Monday by the firm.

The complaint, filed in New York state court, is the first detailed account explaining why Kasowitz Benson says it fired Jeremy Pitcock, an IP litigator who joined from Simpson Thacher & Bartlett in 2006. Pitcock denies sexually harassing anyone, let alone having engaged in a pattern of sexual harassment.