Amazon's one-day delivery advertisement for Prime members has been banned due to it being perceived as misleading.
The UK advertising regulator explained that it had received 280 complaints, mostly from Prime customers who reported not receiving their packages within a day.
They have said the ad must not appear again in its current form and Amazon must make it clear that a significant proportion of Prime items were not available for next-day delivery.
A spokeswoman said: "Amazon Prime offers fantastic 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."
Citizens Advice said online retailers should provide easy access to compensation if they fail to deliver items on time.
Chief Executive Officer of Citizens Advice, Gillian Guy said: "We've found 40% of people who used a premium delivery service received their parcel later than expected.
"It's more difficult for consumers to work out what they're owed when their parcels don't arrive on time if they've paid for a service like Amazon Prime, compared to when they pay for one-off deliveries."
