The EU aims to announce whether Amazon's data practices will be investigated further in the coming months, the institution's competition chief told CNBC.

In September, Margrethe Vestager, the head of competition policy in Europe, opened a preliminary probe into Amazon's use of data on its third-party merchants. The idea was to assess the dual role of the e-commerce giant, given that it hosts but also competes against these other merchants. There are concerns that Amazon could be using sensitive information about its competitors' products to its own advantage.

Speaking to CNBC on Tuesday, Vestager said that the investigation is now at an "advanced" stage. "A lot of businesses have taken time and effort to give us data to answer our questions. So, we very carefully go through this. But as I said we are advanced, and I hope that we can sort of conclude the first phase within this mandate," she said.