According to allegations published in the Wall Street Journal newspaper, independent sellers were able to delete negative reviews, while they were also given the opportunity to restore some banned accounts.
Responding to the allegations, Amazon insisted it had a "zero tolerance" policy in place.
A spokesperson added: "We hold our employees to a high ethical standard and anyone in violation of our Code faces discipline, including termination and potential legal and criminal penalties."
The allegations come shortly after it was revealed that a group of Amazon employees were being paid to defend the tech giant on Twitter.
The company has previously faced intense criticism over some of its working practice, which has served to damage the image of the Amazon brand, and last month it emerged that a group of employees have been encouraged to defend and promote the company on the micro-blogging platform.
A spokesperson for Amazon explained: "The most important thing is that they've been here long enough to honestly share the facts based on personal experience.
"It's important that we do a good job of educating people about the actual environment inside our fulfilment centres, and the FC ambassador programme is a big part of that."