Marks & Spencer has begun stocking Jersey butter in 350 stores following a deal with Jersey Dairy.
The in-store launch, which began earlier this month, was timed to coincide with the Jersey Royal potato season.
Jersey Dairy supplies butter products to a number of independents, but the M&S deal is the first time it has supplied pack butter to a multiple retailer.
The products are being presented in distinctive black and cream packaging that explains the butter's origin and says the product is 'fantastic with Jersey Royal potatoes'.
"We looked at several producers, but concluded that it had to be the real thing: butter from pedigree Jersey cows reared and fed on the island of Jersey," said an M&S spokesman.
Jersey Dairy applied for European PDO status for Jersey butter in December, sparking concern from producers outside the island. Defra put the application out for public consultation two weeks ago.