The firm has stopped taking orders on its website and apps, including for food and clothes.
Marks & Spencer (M&S) says it has stopped taking online orders as the company struggles to recover from a cyber attack.
Customers began reporting problems last weekend, and on Tuesday the retailer confirmed it was facing a "cyber incident".
Now, M&S has entirely paused orders on its website and apps - including for food deliveries and clothes - and says it will refund orders placed by customers on Friday.
The firm's shares fell by 5% following the announcement, before recovering.
Online orders remained paused on Saturday morning.
"We are truly sorry for this inconvenience," the retailer wrote in a post on X.
"Our experienced team - supported by leading cyber experts - is working extremely hard to restart online and app shopping.
"We are incredibly grateful to our customers, colleagues and partners for their understanding and support."