The warning followed chaos at a First Milk’s Lake District Creamery in Aspatria, Cumbria, as milk producers queued up in the hope of gaining a contract.
Marshalls were called in to control crowds, according to a First Milk spokesman.
He said the processor had already recruited 300 members from DFoB since Thursday, but time was running out, with books expected to close soon.
Of about 300 new members signed up, about 100 were within the catchment for First Milk’s Lake District Creamery, the co-op said.
First Milk is understood to be offerng farmers a standard litre price of 22.03p.
For more information on First Milk contracts call 0141 847 6800.