John Lewis's "Never Knowingly Undersold" pledge has been called into question following an investigation that claims it did not drop prices on products it knew were being sold cheaper elsewhere.
Consumer website MoneySavingExpert.com (MSE) said the department store did not drop its advertised prices on 15 of 16 products it was informed were being sold for less by rivals, even though it agreed to pay out individual price match refunds.
The John Lewis website promises that: "Our dedicated price-monitoring team proactively check the prices of branded products at our high street competitors every day, including online and during sales. If we find that they are selling the same individual product, sold with the same service conditions, at a lower price, we'll meet that price in our shops and at johnlewis.com.
"So we don't expect you to find a lower price elsewhere. But if you do, you can easily make a price match request."
MSE said its researchers bought a range of items, all of which were cheaper elsewhere, over two consecutive days in March, from a number of different John Lewis stores and its website.
They then monitored the price of 16 items John Lewis had agreed to issue price match refunds on, therefore accepting its price had been undercut, but said the retailer only cut the price of one of the items over the next seven days.
A final check of johnlewis.com 14 days after the purchases found it was still being undercut on 10 of the original items.
MSE said John Lewis admitted some of the products had simply been missed by its monitoring team, though argued other price matches were approved for individuals, but the store prices on these items had not been dropped because competitor stores were not within eight miles.
MSE founder Martin Lewis said that while the store's service is "generally right up there, our research shows John Lewis is not always the champion of price it wants people to think it is.
"After all, if it is agreeing to reduce prices because they qualify for its price match as they are cheaper elsewhere, and then continues to sell the same goods at the higher price to everyone else, it knows that it is being undersold elsewhere.
"If John Lewis wants to tout its 'Never Knowingly Undersold' catchphrase, it should put up or shut up, or it risks losing its great reputation."
John Lewis said: "Never Knowingly Undersold is at the heart of everything we do and we are disappointed that MSE focused on a small number of specific examples rather than the millions of prices that we lower each year.
"We will look at the detail of their report to see where we can make improvements for our customers in either our processes or communications on the website."