Centaur, which is listed on the Alternative Investment Market, has seen its share price drop from 155p a year ago to 82p on Friday, valuing it at £118m.
Graham Sherren, chairman and founder, owns a 5.9% stake in the company.
Last year, Centaur, which also owns Money Marketing and Period Living, made an operating profit of £15.9m on turnover of £90.3m.