Trade at John Lewis’ flagship London Oxford Street store was hit by failures at its tills last week as shoppers flocked to the store in the important Christmas trading period.

John Lewis, famed for its high levels of customer service, said it was investigating the failures but described the problem as “sporadic”. The department store chain played down the software glitches at its flagship branch during a week when it recorded its best ever week of sales.

Customers were being redirected to alternative tills at the store on both Saturday and Sunday, and a source told Retail Week that the problem had been ongoing for a week.

The source said: “People are walking out of the store because the tills keep breaking down and takings are down quite a lot. The tills can’t keep up with the number of customers and keep overloading.”

A spokeswoman for John Lewis said that while trade was affected last week in Oxford Street, trade this week is up on last year by more than its other London branches.

The store has four separate till systems at the branch as a contingency, so if a problem occurs customers can pay at a different till point.

The spokeswoman added: “The issue is a software problem, which means that sporadically some tills have problems with some types of payments. However, even when there is a problem we have always been able to take all payment methods including Visa, on the majority of our tills.

“When the problem occurs we have partners on hand to advise customers where is the best till to pay via their chosen payment method. As ever at this time of year, partners from head office help out on the shopfloor so Oxford Street has extra support to maintain service levels.”

Retail systems consultancy Retail Answers managing director Mike Eaton said the situation was “upsetting” for customers and staff. “Customers can be directed online instead but you run the risk of them going to a competitor,” he said.