Britain’s biggest supermarket chain Tesco this morning reported a fall in half-year profits for the first time in around two decades.

Pre-tax profit for the six months to 25 August was £1.7bn, down 11.6% from the same period last year.

The retailer is in the middle of a £1bn investment programme to improve its stores in the UK, which was announced by chief executive Philip Clarke in April.

Earlier this year Clarke revealed a six-point plan to overhaul the supermarket, which includes a scheme to grow its workforce by some 8,000 people.

This morning, Clarke explained: “We continue to act decisively to tackle challenges and seize opportunities across the group. In April, I set out our plans to ‘Build a Better Tesco’ in the UK.

“We have been hard at work and I am encouraged by our customers’ initial responses to the changes we have made – but there is much more to be done. I am pleased that the team is in place, highly focused and energised, and I want to thank them for everything they have done.”

He concluded that the external environment “continues to present challenges” all over the world.