Hack fallout Every day costs chain millions in lost sales

Unusual activity on tech systems over Easter was the first sign of a sustained cyber-attack on Marks & Spencer, which is costing the retailer millions of pounds a day.

- Sarah Butler Dan Milmo

The group, the UK's biggest clothing retailer, which accounts for a third of underwear sales alongside food and homewares, has now been forced to stop taking online orders for more than a week - with little hope of rebooting them in the short term.

Stores are also struggling to keep shelves full with automated stock systems offline and at one point this week staff were manually checking fridge temperatures amid concerns about digital monitoring systems.

After days of disruption, contactless payments and gift cards are now being accepted, refunds are now possible and returns are being processed in clothing and homewares stores. It is also possible to pick up online orders made before 23 April. The Sparks loyalty scheme remains disrupted, however.

M&S first reported problems over the Easter weekend, when it stopped taking click-and-collect orders and its contactless payments were affected. While those have restarted, problems continue across the business with the company having to pause deliveries of some packaged food items to Ocado, the online grocery specialist it co-owns.

The Metropolitan police have confirmed they are investigating a cyber-attack with the help of the National Crime Agency. A hacking collective known as Scattered Spider has been linked to the hack.