Underwoods Motoring, which has locations across Essex and Suffolk, will now only sell used cars and provide garage services.
The car dealer, which began trading in 1981, cited a number of changes with its manufacturer partners.
It wrote on its website: “Like all things, change is inevitable.
“With major changes in the way that motor manufacturers wish to operate with their appointed dealer representation, Underwoods too must change.
“We are moving away from representing car manufacturers as their appointed Main Dealer for New and Approved Used Cars.
“We are also leaving our Colchester location, which you will be pleased to hear will continue as automotive dealers, but with new management and brands.”
It added: “We will continue to hold Authorised Repairer Status for Vauxhall, Ford, Skoda and Kia, allowing us to provide Warranty support for these brands, as well as day-to-day garage services including; Servicing, MOT (inc. Class 7) and Repairs at our Bodyshop.
“We are dedicated to providing the best service and continued support to all drivers we have supplied vehicles to.”
It comes after Underwoods closed its Skoda dealership in Colchester after representing the Czech brand for more than 19 years.
Just a fortnight later in April, the dealer group revealed its Vauxhall dealership in the Essex town was closing.
Underwoods had represented the British car company there for more than 25 years.
It also lost Kia in the town, with its showroom closing on April 29.