The co-op said stock availability at its stores will not increase until the end of this week as it strives to recover from a cyber attack two weeks ago.

Grocery Mutual Aid at the funeral said it was in the “recovery phase” and “working closely with suppliers to restock our stores” after re-opening its stock ordering system. The system was shut down as part of an effort to defend against cyber attacks.

Shoppers complain about having empty shelves in partnership stores with rural communities, especially in Scotland, as the group’s grocery stores are often the only major food stores a few miles away, facing special difficulties in obtaining basic supplies. The team had previously said an emergency system has been established to prioritize stores at such locations.

It also said last week that despite the disruption, it “in the cabinet essentials to add horizontal flow to fresh, frozen and frozen products”.

A spokesperson for the cooperative said: "After a malicious third-party cyber attack, we have taken early and decisive actions to limit access to our systems to protect our cooperatives. We are now in the recovery phase and are taking steps to gradually restore our systems online in a secure and controlled manner."

It says all payment methods, including contactless and chips and PIN, work in its stores.

The co-op said earlier this month that hackers had accessed data related to "large amounts of customers" from one of the systems. Information includes name and contact information. It does not include passwords or financial information, such as bank or credit card details.

The hacker emerged within days of a similar attack on Marks & Spencer, where the company was forced to shut down its website and handle low inventory in some stores as it resolved the incident, while luxury department store Harrods was forced to shut down certain systems after being hit by a cyber attack.

M&S revealed Tuesday that it had acquired some personal information related to thousands of customers in a cyber attack that has weakened its online operations for more than three weeks.

The retailer said some customer data has been accessed, but that does not include available payment or card details or any account passwords. The details obtained are the name, address, date of birth and order history.

The co-op and M&S are expected to have fines for stealing customer data from the system in addition to losing sales.

According to a report from the Financial Times, M&S's cyber insurer could claim £100 million from its cyber insurer, which is much more than analysts had previously expected.