All Siri voice-commands are stored on an Apple database for up to two years, according to a report from Wired.
As privacy concerns were raised, Apple confirmed the reports, adding that the data is anonymised after six months.
After receiving a voice-command, Apple assigns a random identifying number to the data so that it can be analysed. Six months later the number is disconnected from the voice file, and eighteen months later the data is deleted.
Apple spokeswoman Trudy Muller explained to Wired: "Apple may keep anonymised Siri data for up to two years. If a user turns Siri off, both identifiers are deleted immediately along with any associated data."
She added that Apple only uses your voice data to test features and make upgrades.
However, speaking to The Register, Nick Pickles, director of pressure group Big Brother Watch, has said that Apple needs to be open and honest about what it does with these queries.
He said: "There needs to be a very high justification for retaining such intrusive data for longer than is absolutely necessary to provide the service,"
"Apple need to come clean and say what they are storing, for how long and most importantly, why. As consumers become increasingly concerned about their privacy, companies cannot afford to keep their customers in the dark about what happens to information."