The agency will now produce a new strategy and ad campaign for the helpline, which encourages people to claim compensation after an injury.
It is understood that the company wants to revamp its approach to marketing and focus on its expanded offering of legal services and advice, rather than just emphasising its "no win, no fee" model.
The National Accident Helpline, which has used the Direct Response Television Centre to produce its campaigns in the past, previously focused its advertising on real-life examples of claimants who have won compensation following an accident.
However, its most recent campaign, which launched in December last year, marked a step away from this approach, featuring a woman explaining the benefits of the service alongside slow-motion images of a car accident.
The National Accident Helpline is owned by the private equity company LloydsTSB Development Capital.