Morrisons has said it is to close 132 McColl's stores, risking 1,300 jobs, following the supermarket's purchase of the convenience chain.
Workers potentially impacted by redundancies are to be offered other jobs within the business, Morrisons said.
The supermarket had agreed to buy McColl's out of administration in May. It plans to convert McColl's stores into Morrisons Daily shops as part of efforts to improve the finances of the company.
The deal was, at the time, said to save all 16,000 McColl's jobs and stores.
Many McColl's already operate as Morrisons Daily stores. Of the 1,164 McColl's stores trading, 286 come under the Morrisons Daily brand.
The 132 shops, 55 of which have a Post Office counter, are to be closed throughout the coming year.
The stores are loss-making and have "no realistic prospect" of recovering, Morrisons said.
It will mean within two years when the conversions are completed there will be more than 1,000 Morrisons Daily stores.
The closure of shops with Post Office counters won't begin until 2023 to facilitate Christmas trade to give the Post Office time to make "alternative arrangements", Morrisons said.
The McColl's acquisition was last week cleared by the competition regulator.
The number is fewer than the 35 areas in which the Competition and Markets Authority has raised concerns over.
Speaking after the deal was cleared by regulators, Morrisons' CEO David Potts said they would now "begin the urgent journey to transform McColl's into a viable, well-invested and growing operation".
"We very much regret the proposed closure of 132 loss-making stores but it is, very sadly, an important step towards the regeneration of the business," Joseph Sutton, director of Morrisons wholesale, said.
McColl's has an annual turnover of £1.2bn and accounts for about 0.8% of the UK grocery market.