Although Amazon’s sales have been booming with Prime Day seeing an increase in revenue year-on-year, the e-commerce retailer has come under fire from the Advertising Standards Agency (ASA), which said Amazon’s advertising of a one-day delivery service for Amazon Prime members was “misleading”. The ruling, which is to be obtained by The Times and announced later this week, has come after 270 people complained about not receiving their items by the next day.

The ASA has claimed that Amazon has been “misleading” consumers by promoting one-day delivery ads as part of its premium Prime subscription service. It turns out, however, that delivery option was not available for a significant proportion of Prime labelled items. The advertising watchdog has now said the company’s ads “must not appear again in its current form” as a result.

“When a significant proportion of Prime labelled items were not available for delivery by the subsequent day with One Day Delivery, we concluded that the ad was misleading,” said the ASA; “Because consumers were likely to understand that, so long as they did not order too late or for Sunday delivery, all Prime labelled items would be available for delivery the next day with the One Day Delivery option.”

An Amazon spokesperson commented that Amazon Prime currently offers benefits to members, including “one-day delivery on millions of eligible items at no extra cost.”

“The expected delivery date is shown before an order is placed and throughout the shopping journey and we work relentlessly to meet this date. The overwhelming majority of One-Day Delivery orders are delivered when promised,” they said.

Amazon claimed last month that this year’s Prime Day was the biggest shopping event in Amazon history with desktop display ads accounting for 54% of ad impressions leading up to the annual shopping event.