Andrew Higginson, finance director, said: “We have had to work hard to deliver the first-half numbers and clearly life isn’t getting any easier.”

If oil prices remain at their current level, costs for the year could exceed budget by up to £60 millon, while consumers’ spending power was also likely to be hit by higher energy and fuel costs, he said.

Mr Higginson said that, given that Tesco had already budgeted for a significant rise in costs this year, it would be hard to offset all the extra costs through efficiency savings.

The news cast a shadow over another very strong set of figures from Tesco as the supermarket continues to hammer rivals with a 6.6 per cent rise in underlying sales in the three months to August 13, against 6.8 per cent in the previous quarter. Total sales rose 14.1 per cent to £18.8 billion in the six months to August 13, helped by an increasingly strong international business.

Weekly customer visits rose by three million, compared with a year ago, and average spend also rose, despite a 2 per cent fall in Tesco’s prices.

Pre-tax profits rose 18.7 per cent to £908 million. However, profits in the personal finance division, a key part of Tesco’s growth strategy, stagnated because of higher provision for bad debt and a very competitive motor insurance market.

The generally more downbeat statement surprised analysts, who have become used to Tesco overshooting consensus profit forecasts.

Andrew Fowler, Tesco’s broker at Merrill Lynch, said in a note: “To read that oil-related UK costs are £60 million ahead of full-year budget, eating up about 20 per cent of group profit growth is stark. It should all come as no surprise given the newsflow from the general retail sector, but it somehow feels worse coming from Tesco, which has been immune.”

However, analysts pointed out that the £60 million in extra costs was a fraction of Tesco’s expected £3.25 billion costs in the second half.

Sir Terry Leahy, Tesco’s chief executive, said that he was more “optimistic” than some of his retail rivals about the outlook for the next six months. He said: “We can see from our sales figures that we have a strong business and we have got plenty to do. We can see consumers are more cautious — when we poll customers, confidence is lower — but it is not at a record low.”

Sir Terry said Tesco is budgeting for a 3 to 4 per cent rise in underlying sales, as it has for the past few years, but added: “Now more than ever it seems an appropriate kind of range.”

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