Budget supermarket Kwik Save will go into administration tomorrow after a Manchester high court judge accepted a proposed refinancing package.
More than 90 stores will be closed as part of the arrangement, with a further 56 being transferred to a new company.
Retail union Usdaw said its members were "utterly devastated" at the news after forgoing wages for the last six weeks in a bit to keep the company afloat.
The union claims that workers at the 56 stores, which will trade under the name Fresh Express, will be retained on their agreed rates, but that hundreds of other employees will have to apply for statutory protection through administrators KPMG.
Kwik Save used to be owned by Somerfield but in recent years has seen its market share shrink in the face of competition from Aldi and Lidl, as well as budget food lines from larger retailers Tesco and Asda.
"Usdaw members have been working for nothing for the last six weeks enduring great hardship in the hope that their sacrifice would help save the company so staff in the stores earmarked for closure will be utterly devastated," commented Usdaw national officer Joanne McGuinness.
"At this stage we have no firm information which stores are to close and which are to transfer but as soon as we know we will inform our members.
"Our members have shown incredible strength and resilience in trying to keep the company alive and they have told us they have had to rely on handouts from relatives to put food on the table and some have faced losing their homes."