Patrick Sookhdeo of the Barnabus Fund is accused of groping a female in his office in February last year and later intimidating witnesses.
Swindon Crown Court was told how the 68-year-old asked the woman if he could trust her before inappropriately touching her.
The alleged victim, who can't be named, said the incident made her frightened, physically sick and prevented her from sleeping.
Mr Sookhdeo has been campaigning on behalf of the persecuted church for many years. He's written extensively on Islam and interfaith relations.
He denies the accusations. The trial continues.