Bisdee, who was the company's first marketing director, has left to pursue other business interests. It is not clear whether he will be replaced.
He joined from interactive TV betting firm Blue Square in July last year, as part of a launch team that included C4's in-house creative team 4Creative and OMD UK (Marketing, July 19).
Attheraces, previously known as Go Racing, is a consortium made up of racecourse owner Arena Leisure, BSkyB and Channel 4. In June last year it successfully bid £307m for the multimedia rights to coverage of races from 49 of the UK's 59 racecourses for a ten-year period.
Bisdee had the task of developing Attheraces as an integrated brand that could work across terrestrial and digital TV, the internet and 3G mobile technology.
The live racing and betting web site at www.attheraces. co.uk launched in December last year and in September this year reported a turnover of more than £1.8m since launch.