Fiat, Ford, Kia, Mazda, Mitsubishi, Skoda and Suzuki dealer Border Cars is filing for administration, said its boss Mike Fusco.
He said he has tried to keep the business afloat but it has become less and less viable.
"It has become impossible to trade normally. Two weeks last Tuesday, with no notification at all, one of the franchises terminated me, and took the keys for that franchise. Within four days, every franchise had done the same."
It has six dealerships in Carlisle, Dumfries, Stranraer and Workington, and has traded for 42 years.
Fusco said the company has made half of the 200+ staff redundant and more jobs are likely to go in the next few days.
"Trading has been very difficult over the last few years and it's been getting more and more difficult," he said.
Fusco said "something spooked" the franchise partners.
"With ongoing rising costs, and the tough retail climate for the industry, it is with the greatest of reluctance that we are unable to continue trading," he said.
He said he has poured every penny he has into the business to try to save it.