Amazon asked some advertisers to increase spend on Prime Day by at least 100%

Debbie Ellison, the chief digital officer at marketing agency Geometry U.K., said that one of its clients was asked to at least double its ad spend for Prime Day.

“One of our CPG (consumer packaged goods) clients was asked recently by Amazon to increase its budget by a minimum of 100% to ensure that it did not lose market share during this key sales period. In the case of this client, its products are not natural deals for Prime Day so taking part would only reduce their overall margin,” she told CNBC by email. Geometry advised the client not to increase its ad spend for the shopping event.

“Brands which over-invest in ad spend during Prime Day tend to sit in the electronic & computing and beauty & personal care categories, where they typically achieve between a 50% and 60% sales uplift during this time,” Ellison added.