The John Lewis Partnership slumped to a first half loss of £99m largely driven by soaring inflation which prompted customers to spend less in its stores.

Inflation also hit costs, as the department store group warned of a “highly uncertain” outlook in the run-up to the key Christmas sales period due to the cost of living crisis.

The group, which is staff-owned and includes the Waitrose supermarket chain, made a profit of £69m in the same period of the six months to 30 July last year.

“No one could have predicted the scale of the cost of living crisis that has materialised, with energy prices and inflation rising ahead of anyone’s expectations,” said Sharon White, chair at John Lewis Partnership. “As a business, we have faced unprecedented cost inflation across grocery and general merchandise.”

JLP warned the outlook for the rest of the year was “highly uncertain owing to the cost of living crisis and its impact on discretionary spending as well as criticality of our Christmas trading period”.

The group also announced additional support for its staff, known as partners, including a one-off cost of living support payment of £500 for full-time workers.