Fast Track one of the leading sports marketing agencies in the country and boasts clients such as L'Oreal, HSBC and Carlsberg.
This year it has worked with Olympic and Paralympics sponsors BT and G4S, among others.
The agency was voted Marketing magazine's Sponsorship Agency of the Year in 2011.
Last year, Fast Track lost one of its flagship clients, UK Athletics, which ended its 14-year association with the agency.
Fast Track had previously organised UK Athletics' flagship televised events, including the Diamond League meeting at Crystal Palace.
Fast Track was behind the £50m, six-year deal that UK Athletics signed with Aviva back in 2006.
It is understood the staff exiting the sponsorship agency were primarily involved in Olympic-related work, who had previously worked on the UK Athletics account. Fast Track has around 150 staff, mostly based in the UK.
One rival agency said the agency was axing 30% of its staff, but this was refuted by Fast Track.
Andy Westlake, chief executive of Fast Track, said: "Like many businesses in our sector, we have been looking very closely at the shape and structure of the business after the Olympics and Paralympics Games for some time, to ensure we continue to deliver the award-winning service we have achieved with our many clients and to build our reputation as the Sponsorship Agency of the Year."