Apparel is now the fastest-growing category on Amazon.com in terms of number of units sold, just four months after its launch.

A company spokesman told InternetRetailer.com that: "Apparel's success validates our belief that customers would accept a wide range of offerings from Amazon.com."

Amazon now offers more than 500 apparel brands, and among its best-sellers are children's wear, maternity wear, and big-and-tall sizes.

The online retailer is now in the process of expanding the number of apparel brands that it sells, and is already preparing for the back-to-school selling season in the autumn.