Amazon will begin charging its Prime members for same-day delivery on selected orders from next month in a bid to “improve the service”.

The retailer informed customers via email that the changes will come into place from September 18. It will charge Prime members an additional £1.99 per delivery for orders under £20.

The retailer said both Prime same-day and overnight delivery for orders of more than £20 will “automatically be delivered to you using the fastest available options” at no extra cost.

Amazon’s same-day delivery service means shoppers can receive eligible orders either on the same day or by 1pm the following day at the latest, depending on when orders are placed.

The retailer added that one-day delivery for Prime members remains unchanged and the delivery fee for non-Prime members will remain £5.99 per order.

Amazon said in an email to shoppers: “As we invest to improve our same-day delivery service we are writing to let you know about an update to the same-day delivery options available for Prime members in eligible postcodes.

“The majority of Prime members currently receive most of their Prime orders within one-day delivery, while free same-day delivery can be manually selected for eligible orders.”

A spokesperson for Amazon told Retail Week: “Prime members enjoy fast, free one-day delivery on millions of items.

“We are constantly innovating to deliver a wide selection of great value products at the fastest speeds, and more than a million items are now available for same-day delivery in the UK. Prime members can receive Same-Day deliveries where available for free on select orders over £20, or for £1.99 if the total order is below £20.

“All orders will now be delivered to Prime members with the fastest available free option by default.”