Dairy Crest has announced plans to close its 130 million-litres-a-year Totnes plant.
The Devon site supplies fresh milk to retailers in the region as well as to Dairy Crest's doorstep customers. But a strategic review of the company's fresh milk assets concluded that closure was the best option for the plant.
"To have a viable future, Totnes would need to be modernised and expanded, but expansion is just not possible," said a spokeswoman. "The site is land-locked - it has a railway on one side, the River Dart on the other and houses on the third side."
The retail milk - about 100 million litres of it per year - will be trucked up the motorway to DC's Severnside plant in Gloucestershire for processing and bottling.
And the 30 million-litre doorstep milk requirement will be processed at Hanworth, outside London.
The closure could lead to more than 200 jobs being lost, prompting an angry response from the T&G.