Amazon is set to be told by the UK’s advertising regulator to stop claiming that it guarantees next-day deliveries through its Prime subscription service.

The online giant says it operates an “unlimited one-day delivery” service for its members, but the Advertising Standards Authority is poised to crack down on that claim after complaints from hundreds of customers in the run-up to last Christmas.

According to The Times, the ASA’s ruling, due this week, will say that a “significant proportion of Prime-labelled items were not available for delivery the next day” and will conclude that Amazon’s advertising is “misleading”.

It comes after around 200 customers claimed Amazon’s Prime service, which costs £79 per year or £7.99 a month, failed to live up to delivery pledges in the golden quarter last year.

A spokesman for the ASA said: “We have been formally investigating Amazon’s ‘one-day delivery’ ad claims and will publish our findings in full soon.”

An Amazon spokesman said: “The expected delivery date is shown before an order is placed and throughout the shopping journey and we work relentlessly to meet this date.

“A small proportion of orders missed the delivery promise last year during a period of extreme weather that impacted all carriers across the UK.”

Under fire

Amazon has come under fire from the ASA before. In 2016 the regulator ruled that the etailer’s free delivery claims “did not make sufficiently clear which items were eligible for free delivery, and under what terms, and that they were therefore misleading”.

The online Goliath has also been attacked for its tax payments after its bill was slashed last year despite tripling its profits.

Last week Chancellor Philip Hammond hinted at ushering in changes to the tax system “to ensure that the high street remains resilient” and to create fairness “between businesses doing business the traditional way, and those doing business online”.