Kinect-controlled Xboxes are always alert, silently waiting for commands such as Xbox turn on or instructions.

London – Millions of Britons are being spied on in their homes by Microsoft’s voice-activated Xbox game consoles, Apple smartphones and other hi-tech gadgets.

The revelation comes after Samsung’s admission that its internet-linked smart TVs could be listening in on householders’ private conversations.

Yesterday it emerged that some Microsoft and Apple gadgets, and Samsung’s smartphones, are also snooping on customers.

Microsoft’s Xbox games consoles – used in 84million households worldwide – are among the worst culprits, especially if they are used with one of the company’s popular Kinect devices, which allow users to control the consoles with spoken commands or by moving.

Kinect-controlled Xboxes listen to everything around them, silently waiting for commands such as ‘Xbox turn on’ or instructions to load up computer games including Tomb Raider or Halo.

The technology means people can play games or watch catch-up TV without using the remote control.

But this convenience comes at a price: The device is ‘listening’ to the conversations people have at home every day, regardless of whether it has been switched on or is in stand-by mode. Renate Samson, of the privacy campaign group Big Brother Watch, said: ‘It is a complete invasion of privacy.

‘If every product has the capability of hearing what we say, that stops us being private within our own homes. I don’t think consumers know enough about it. Companies making these products need to think about privacy and security as a priority.’

Microsoft’s Kinect gadgets are so sophisticated and pervasive that Britain’s telecommunications security agency, GCHQ, is even said to have considered using them to monitor families.

Like most gadgets that use voice recognition, Xboxes controlled by Kinect record what people say then translate that information into text commands so that the device knows what to do. Simple commands such as ‘Xbox turn on’ are recorded and processed on the spot, but more complicated instructions are sent to powerful remote servers, often thousands of miles away, for translation.

Microsoft said its customers can stop Kinect listening by unplugging it.

It added: ‘If you use voice-enabled features, we don’t share any data with third-party partners, nor is it used for marketing or advertising purposes.’

The firm is not the only technology giant effectively listening in to people’s private conversations. Apple also records what people say when they press a button on their iPhones or iPads and issue a command to its voice activation service Siri. As with Samsung’s Smart TV and Microsoft’s Xbox, complicated requests are dispatched to remote servers for processing.

Apple makes the information anonymous by allocating it to a randomly-generated number, which is different to the user’s phone number. But it then stores the data so it can learn more about users’ preferences and speech patterns. According to a source, the American firm hangs on to the information for up to two years.

Samsung’s snooping habits also extend further than its smart TVs. People with its S Voice smartphone app – installed by default on devices such as the Galaxy range – could also find their private conversations are being listened to.