Amazon’s Alexa is supposed to listen only when you call her name but she could soon be getting a lot nosier, with plans to eavesdrop on conversations and “whisper” shopping suggestions.

The internet shopping giant has filed a US patent for a “voice-sniffing” system that it would use to monitor whole conversations where users had not actively chosen to talk to their digital assistant.

An algorithm would listen for trigger words, such as “love”, “enjoy”, “hate” or “returned”, and analyse the sentences that followed to build complex profiles of people’s likes and dislikes. The data would be used to recommend products.

Alexa is Amazon’s virtual assistant that responds to voice commands. It can answer questions, play music and control lighting in the home. It was