The computing giant is concerned that spoken queries are being stored in the iPhone firm's data centre in Maiden, North Carolina, Technology Review reports.
Apple's iPhone Software License Agreement appears to confirm IBM's fears, stating: "When you use Siri or Dictation, the things you say will be recorded and sent to Apple in order to convert what you say into text."
By agreeing to the company's terms and conditions, users grant Apple and its agents the right to the "transmission, collection, maintenance, processing and use of this information", including voice input and user data.
Google has also come under fire in recent months for its privacy practises and the way it uses customer data. Last month, the search engine firm introduced controversial changes to its privacy agreement, sparking criticism from across the tech industry.
Apple's Siri made the headlines last week following reports that a loophole in its search protocol was causing it to recommend the rival Nokia Lumia 900 smartphone.