Four ads for electronic items on Amazon have been banned for using "misleading" recommended retail prices (RRPs) and savings claims.
The ads, seen in July last year for a television, gaming monitor, laptop and electric toothbrush, all listed RRPs and savings of up to £300.
Each ad received a single complaint that the savings were misleading and unsubstantiated.
Amazon said they checked that the RRP was in line with the prices displayed on third-party websites and as sold by third-party sellers on its Marketplace site, and said their retail prices fluctuated constantly because they sought to meet or beat the lowest competitive price for customers.
However, it said the RRP claim in the ad for the television was "made in error" and said it was working on a solution to avoid similar mistakes in future.
Regarding the electric toothbrush, which was listed as having an RRP of £270 but was a "Deal of the Day" at £84.99, Amazon said their checks showed that the product was priced at £270.00 by third-party retail websites for 14 out of the 21 days that had passed in July before the complainant saw the ad.
The Advertising Standards Authority (ASA) said that consumers would understand the reference to an RRP to mean that the advertised product was generally sold at the stated price across the market.
It found that the gaming monitor, listed with an RRP of £752 but available for a £193 saving at £559, was sold over the six weeks prior at the higher price for nine days, then at a lower price for 14 days, then again at the higher price for two days, and after that, at a lower price for 16 days.
The ASA said the price fluctuations "did not demonstrate that Amazon usually sold the product at the higher price of £752.00".
It also found that the data Amazon provided to support the RRP claim in the ads for the laptop and the electric toothbrush "was not sufficient to demonstrate that the product was generally sold at that price across the market".
The ASA ruled that the ads must not appear again in their current form, adding: "We told Amazon to ensure that future references to RRPs reflected the price at which the products concerned were generally sold, and to ensure that they held adequate evidence to substantiate their savings claims."
An Amazon spokesman said: "Our customers come to Amazon and expect to find low prices and incredible deals, and we work hard to provide both all year long. "