Dairy Farmers of Britain (DFOB), which employs 2,200 people and is responsible for 10% of UK milk production, has appointed receivers.
DFOB is an agricultural cooperative with 1,800 member farmers who supply over one billion litres of milk a year.
Its workers are based in Blaydon, Nantwich, Lincoln, Llandyrnog, Bridgend and Lubborn.
The receivers are trying to sell the cheese and milk businesses as well as maintaining milk collections.
"What is most important now is that the supply chain is maintained through to our consumers, that jobs are saved, and that there is a home for our members' milk," said Lord Grantchester, chairman of DFOB.
The cooperative closed its Fole and Portsmouth dairies in November last year but it has struggled to pay its member farmers a competitive price for their milk and large numbers of them have been resigning.
DFOB has lost the milk contract from Co-operative supermarkets, which has made the restructuring process so far inadequate.