Google is reportedly enlisting the help of its Motorola subsidiary to build its rumoured smartwatch, Digital Spy said.

Android Authority claims to have heard from an inside source that the wearable tech product already exists in prototype form, having been glimpsed in the web giant's Manchester, Berlin and Mountain View offices.

The report also states that the Google watch is not yet a standalone device, requiring smartphone tethering to function properly, in a similar fashion to Google Glass.

Motorola has previously dabbled in the smartwatch sector, releasing the Motoactv fitness tracker in 2011, a heart-rate monitor with GPS and MP3 playback capabilities.

Google is one of several tech companies believed to be working on such devices, with Apple's much-rumoured iOS smartwatch gaining the most traction in the media.

Google is yet to announce plans to release any wearable tech hardware besides Google Glass.