The mill mainly supplies flour to the group's Hovis bakery in Duke Street, Glasgow.
Premier is concentrating on eight brands it thinks have the best prospects, including Hovis and Oxo.
Hovis introduced the claim as part of its championing of domestic farmers in 2010.
Hundreds of Hovis workers will leave a factory in Birmingham on Wednesday ahead of its full closure next month.
The "power brands" the company is keeping also include Hovis, Bachelors and Sharwood's.
BBC: Premier Foods sells Robertson's and Hartley's for ?200m
Premier Foods, which makes Hovis bread, is to abandon its pledge to use only British wheat in its loaves.
Premier Foods, the maker of Hovis, is cutting 900 jobs at its bread division and is closing two bakeries.
Premier Foods said at the time that it was necessary to pass increases on to retailers, but at one point, Tesco refused to stock some Hovis products.
Some brands are being transplanted into adjacent markets: the new Hovis Breakfast Bake is a whole-grain biscuit that Premier hopes will take some of the growing market for on-the-go breakfasts.
ECONOMIST: A debt-ridden firm tries to breathe new life into old brands
Residents and politicians in Birmingham have reacted with shock to the news that Premier Foods, the maker of Hovis bread, is to close a bakery with the loss of 500 jobs.
David Seeckts, head of manufacturing for Hovis in the Midlands, said it had taken the "unfortunate but difficult decision" to close the Birmingham bakery because the significant contract had been lost.
The archetypal northern terraced houses on a steep hill look like they belong in cult gritty 70s movies like Get Carter or the famous Hovis Advert where the little boy pushes his bicycle up a big hill.
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"This is just another stage in the disaster story that has been Premier Foods over recent years, which has consistently struggled ever since its decision to buy Hovis in 2006, " said Jennie Formby, Unite national officer for food and drink.
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