The FTA has moved its account from Edelman to Citigate Dewe Rogerson Public Policy.
Citigate is charged with lobbying the Treasury as chancellor Alistair Darling comes under mounting pressure to scrap next month's fuel duty rise - as official figures showed pump prices are rising faster than ever.
Citigate's team is being led by Simon Nayyar in London and John Mullin in Edinburgh, both of whom worked for Edelman until leaving the agency last year.
The agency switch comes as the FTA kicks off a recruitment hunt for the new role of director of comms to replace long-serving external affairs director Geoff Dossetter.
Dossetter plans to retire in September.
The FTA is one of the largest trade bodies in the UK with 13,000 members moving goods by road, rail, sea and air.