Amazon is working on a way for its Alexa personal assistant to distinguish between users in the same household based on their voice.

The new feature, currently being work on in secret by the online retail giant, could lead to Amazon's Echo smart speaker ignoring specific commands from certain people, such as a child trying to buy something online. It could also play music from a specific user's music library without being told where to look.

Anonymous Amazon insiders told Time the company is working on a way to distinguish different voices by analysing each person's 'voice print', a unique identifier based on how they speak.

By only replying to commands from certain people, Amazon could prevent repeat scenarios like that of Megan Neitzel, the US woman whose young daughter used Alexa to buy a $170 (£140) doll's house. Neitzel was unaware of the purchase until the large package arrived at her house. With Voice ID, parents couple prevent Alexa from accepting shopping instructions from children or other unauthorised members of the household.

Music playback could also be improved and simplified, as Alexa could learn the tastes of each family member and start playing appropriate music as soon as each person asks. For now, users must command Alexa to switch accounts either with spoken instructions or via a smartphone app.

Just like Siri on the iPhone, Microsoft's Cortana and the assistant on Google phones, Alexa can answer questions about the weather, news and the account holder's calendar. It can also answer questions using information from Wikipedia, but so far there is no way of Alexa knowing who is speaking to her. Indeed, she will often reply when he name is mentioned on a television advert playing in the same room.

According to the report, Amazon has been developing an ability for Alexa to tell voices apart since at least the summer of 2015, over a year before the Echo and smaller Echo Dot went on sale outside of the US. For now, it is unclear if Amazon has successfully developed the technology, or if it will be made available to Echo owners.