Marks & Spencer has said it will lose an estimated £300m as a result of a damaging cyber-attack that has forced it to halt online orders and struggle to keep store shelves stocked.

The number was revealed as M&S said annual pre-tax profits rose a better than expected 22% to £876m ahead of the cyber attack.

The company said it had over £400m of net funds in the bank so that it was “in the best financial health we’ve been in 30 years” ahead of the attack and the expected financial impact would be mitigated by insurance and other actions.

The UK’s biggest clothing retailer, which also sells food and homeware, has been battling to recover for a month since its IT systems were hit over the Easter weekend.

The attack forced M&S to stop orders via its website, through which it sells fashion, homeware and gifts, while deliveries of food and fashion into stores and some deliveries to its online food partner, Ocado, have also been disrupted.

M&S has also admitted that some personal information relating to thousands of customers – including names, addresses, dates of birth and order histories – was taken in the cyber-attack.

The attack, which has been attributed to the hacking collective Scattered Spider, began days before similar cyber-attacks launched against the Co-op and Harrods emerged.

More details soon …