BT, the U.K. telecoms company, has launched legal action in the U.S. against Google for patent infringement in a number of areas crucial to the U.S. technology group's search, maps and music services, as well as its Android phone platform.
BT claims infringement of patents in technologies behind location-based services, navigation and guidance information, as well as access to mobile services and content.
Such patents cover a variety of Google's services, such as music, maps and advertising but also its Android operating system, which is used by more than half of smartphones in the world.
BT has filed a civil suit in a Delaware court alleging infringement of one or more of six of its patents. The company has asked for unspecified damages, as well as for a trial by jury.
Google declined to comment ahead of a formal statement expected later Monday.
In a statement, BT said it had made "a well-considered claim" and that there was "a strong case of infringement."
It said: "BT can confirm that it has commenced legal proceedings against Google Inc. by filing a claim with the US District Court of Delaware for patent infringement. BT's constant investment in innovation has seen it develop a large portfolio of patents which are valuable corporate assets. This is about protecting BT's investment in its intellectual property rights and innovation."
BT has a total worldwide portfolio of about 5,600 patents and applications, and during the last financial year filed for patent protection on 62 inventions.
Over the past five years, BT has spent more than £5-billion on research and development and has a history in mobile telecoms given its Cellnet venture in the 1980s.
BT says that those services that infringe one or more of its patents include the storage, retrieval and delivery of location-based activities of Google's search engine, Android, AdMob, AdSense, Gmail, Google+, Google Maps, Google Offers and Google Location.
It says that Google has derived a substantial value from these products and services and the action aims to recover compensation it is owed and to prevent Google from continuing to use the services without BT's permission.
The case marks a return by BT to a widespread patent battle being engaged in the telecoms industry, which has intensified in recent years given the popularity of smart phones and internet based services by rivals offering often similar platforms.
In particular, those companies that have been established longer are looking to use their large historic patent portfolios to either prevent others using them, or derive some value from them through licensing deals.
However, patent issues are often very complicated and can come down to interpretation given the similarity of many technologies that do slightly different things.
Google is involved in a number of patent disputes with companies such as Apple, Microsoft and Oracle over its Android platform.
Handset manufacturers are similarly involved in complicated legal suits, ranging from fundamental technologies that allow the devices to work to the simple design of phones.
The International Trade Commission is expected to rule Monday in the US on a patent case involving HTC and Apple that had been delayed last week, which also involves Android phones made by HTC. This could also have a wider implication for Google's Android platform should there be a decision in favour of Apple.