Suit retailer has been warned about its sales promotions after the advertising watchdog found some products were discounted for up to five months.
TMLewin.co.uk featured pages of promotions on men's suits and shirts, giving an original and reduced price for each product.
A reader complained to the Advertising Standards Authority (ASA) that the savings claims were misleading because they did not believe that the products had ever been available at the original prices.
TM Lewin said it set the prices of its men's tailoring lines on the website every six months and that those prices were valid for 28 consecutive days, after which time they were discounted.
The retailer said the products were available at the discounted price until they were "price-established" again six months later.
The ASA said the retailer could not demonstrate that all of the suits and shirts on the website had been available at the higher advertised price.
It added that industry best practice said the period of time for which the discounted price was available should not be more than that for which the higher price was available.
It said: "We were concerned that TM Lewin's pricing system meant that the products would be available at the discounted price for a total of five months, which was substantially longer than the period of time they had been available at the higher price, without that being made clear in the ad."
The ASA ruled: "Because TM Lewin could not demonstrate that all of the products had been available at the higher price, and because they did not state the date range for the higher advertised prices when those could have been charged for significantly less time than the discounted prices, we concluded that the ad breached the code."
It ruled that the promotion must not appear again and told TM Lewin "to ensure that they held substantiation for all advertised prices, and to make clear the basis of price comparisons where the discounted price was available for longer than the higher price".