A "flaw" in Google's new voice-activated Home Mini speaker meant some of the devices constantly recorded owners without them knowing.

The new smart speaker is designed to respond to commands when it hears the wake phrase "OK Google". But a flaw in the new speakers meant a few early-release devices would listen to and record their owners constantly.

Google said a "small number of the devices" were affected by the problem, which caused them to think users had pressed the button that can be used to activate them. The issue has been fixed through a software update released on October 7.

"We take user privacy very seriously. We've removed any activity/queries that were created by long pressing the top of a Google Home Mini between October 4 and October 7, when the software update was rolled out. That information will no longer be listed on your My Activity page. You can also always go to your My Activity page and delete any past activity from your account," Google said.

It seems that the affected devices were early releases at recent Made by Google events. Pre-ordered Google Home Mini purchases aren't affected, Google says.

Artem Russakovskii, reporter at Android Police, spotted the flaw in the Home Mini that Google had given him to review.

"The Mini was behaving very differently from all the other Homes and Echos in my home - it was waking up thousands of times a day, recording, then sending those recordings to Google," said Russakovskii. "All of this was done quietly, with only the four lights on the unit I wasn't looking at flashing on and then off."

Amazon's Alexa has faced similar criticism after security researchers discovered a way to install malicious software onto the first version of the device to turn it into a wiretap.