Charlotte EdwardsBusiness reporter, BBC News
The Co-op has said the cyber-attack it suffered earlier this year cost it at least £206m in lost revenues.
The retailer's IT networks were infiltrated by hackers in April, resulted in payment problems, widespread shortages of goods in shops, and the loss of customer data.
Co-op chair Debbie White said the "malicious" attack had caused "significant challenges" in the first half of 2025.
She added the group must now rebuild "better and stronger to meet the challenges and opportunities that lie ahead".
Overall, the retailer reported a £75m underlying pre-tax loss in the six months to 5 July, compared to a £3m profit in the same period a year earlier.
It also said profits were hit by increased staffing costs and regulations, as well as the cyber-attack.
The full cost of the attack could be much higher as the Co-op said it was also expecting there to be some impact to its business in the second half of the year.
April's cyber-attack resulted in empty store shelves and issues with digital payments. The disruption was particularly felt in some rural areas where the local Co-op is the only large supermarket.
After initially downplaying the attack, the Co-op later admitted all 6.5 million of its member customers had their data stolen.
The business's funeral homes also had to resort to paper-based systems.
Co-op chief executive Shirine Khoury-Haq said she was proud of how the business had responded to the attack and that it highlighted many "strengths".
"It also highlighted areas we need to focus on - particularly in our Food business," she said.
The attack on the Co-op came amid a challenging period for the group, as it faces rising costs and and pressure on consumer confidence from the rising cost of living.
Last year, the company reported improved profits but warned in April it would face more than £200m in costs and spending pressures in 2025, including £80m from the impact of shoplifting.