Tesco’s £1bn revamp of its UK store network has fallen massively behind schedule.

Instead of the 430 “refreshes” planned in the past year, just 300 of the UK stores have been revamped under the Building a Better Tesco programme - a shortfall of more than 30%.

Tesco said work on improving many Extras had taken “longer than planned”.

“What became clear is that some of the larger stores were going to need more work than had originally been planned,” said a Tesco spokeswoman.

It has also been working on how to incorporate new features, including the rollout of Harris + Hoole cafes, Euphorium bakeries and Giraffe restaurants.

Clarke said the new features were transforming stores where they appeared and Tesco was determined to speed up the revamp across the entire country, pledging that 70 large stores were in the pipeline for refurbishment this year - though this still represents a shortfall on its original target.

“Some of the decisions taken such as piecemeal investments in Harris + Hoole and Giraffe seem to have complicated the previous ‘back to basics’ strategy that focused on providing better service and store revamps,” said Jon Copestake, a retail analyst at The Economist Intelligence Unit.

Tesco reported a 51.5% drop in pre-tax profits to £1.96bn on sales up 1.3% to £72.4bn for the year to 23 February. UK like-for-likes fell 0.3%. An £804m writedown on its UK property pipeline was accompanied by plans to focus on opening nearly 1,000 new c-stores.