LONDON — Marks & Spencer, one of Britain’s largest retailers, said Wednesday that disruption from a “highly sophisticated” cyberattack that crippled operations over the last month was expected to linger until July and would cost the company about 300 million pounds ($400 million) in lost profits this year.

The breach, which emerged over the Easter weekend, has been costing the company millions of pounds a day after it had to pause online orders, staff had to resort to manual processes and food waste piled up.

Some processes like food deliveries to stores are running smoothly again, but the company is still not taking online orders for clothing and home goods and customers cannot get access to its loyalty program. Online orders and related back-end operations will not fully return until July, the company said.

“This has been a challenging time,” Stuart Machin, the retailer’s chief executive, said in a call with analysts Wednesday.

“We’re now focused on recovery, and customers should be able to shop in our stores as normal,” he said, adding that it would take several more weeks to restart online orders.

Cyberattacks and other digital security breaches are relatively prevalent in Britain, disrupting stores, charities and hospitals. But even when they are contained or interrupted, the damage can last a long time as organizations slowly get processes back online and staff members are diverted from other priorities.

When hackers attacked M&S, the 140-year-old retailer was in the midst of a transformation intended to speed up sales growth and maintain its relevance on Britain’s primary business thoroughfares, known as the high street.

Reduced availability of food has hurt sales, and additional waste and logistics costs will cut into the company’s profit this quarter, the retailer said Wednesday. Sales and profit for clothing, home and beauty items have been “heavily impacted.”

But the final cost of the attack could be reduced by about half after insurance and other efforts to cut costs. The company also said it would use this moment to ramp up an upgrade to its technology within six months, rather than the two years it had planned.