Amazon.co.uk has opted out of the Phorm Webwise deep packet inspection system, used by BT, to target online advertising.
Webwise, developed by UK company Phorm, tracks people's browsing habits via cookies and relays the information to the Internet service provider.
Last week Marcus Williamson, a UK-based Amazon customer wrote to the website's managing director Brian McBride asking for assurances that his history of purchases would not be shared with Phorm.
"I can confirm that we have emailed Webwise requesting we 'opt-out' for all of our domains," McBride replied in an email sent to the customer on Tuesday.
Amazon wasn't immediately available to comment about the decision, beyond confirming that it had been taken.
Google is also considering opting out of Webwise, according to spokesman Bill Echikson.
"We don't do deep packet inspection and we are considering opting out of the Phorm system," he said.
The European Commission opened legal proceedings against the UK government Tuesday for failing to enforce European privacy laws that should have stopped Phorm from covertly testing its data trawling device in 2006 and 2007.
In April last year BT admitted that it had tested Phorm in 2006 and 2007 without informing customers involved in the trial.
BT carried out a new trial of the technology under the brand name Webwise between October and December 2008 but this time it did seek prior consent from subscribers.
The trials resulted in a number of complaints to the UK data protection authority - the Information Commissioner's Office (ICO) - and to the UK police, as well as to the European Commission.
Last month Open Rights Group, a privacy campaign group, went a step further in its fight against Phorm by writing to the world's leading websites, including Google and Amazon, asking them to opt out of Phorm.