British Telecom is claiming billions of dollars of damages from Google in a lawsuit filed in the US which says that the Android mobile operating system infringes a number of the telecoms company's key patents.
The lawsuit, filed in the state of Delaware in the US, relates to six patents which BT says are infringed by the Google Maps, Google Music, location-based advertising and Android Market products on Android.
If successful, the suit could mean that Google or mobile handset makers will have to pay BT royalties on each Android handset in use and which they produce.
That could be expensive: Android is presently the most successful smartphone platform in the world, with its handsets making more than 40% of sales, equating to more than 40m produced every quarter. Google recently said that more than 500,000 Android devices are activated every day.
BT's move – which could also be repeated in Europe – means that Google is now fending off lawsuits against Android from six large publicly-traded companies, according to Florian Müller, an independent expert who follows the twists and turns of international patent litigation. BT joins Apple. Oracle, Microsoft, eBay and Gemalto, a digital security company.
A BT spokesman told the Guardian: "BT can confirm that it has commenced legal proceedings against Google by filing a claim with the US District Court of Delaware for patent infringement.
"The patents in question relate to technologies which underpin location-based services, navigation and guidance information and personalised access to services and content. BT's constant investment in innovation has seen it develop a large portfolio of patents which are valuable corporate assets."
A Google spokesman said: "We believe these claims are without merit, and we will defend vigorously against them."
In the filing, BT cites a number of US patents which were applied for and, apart from one, awarded in the 1990s which it says Android is infringing. BT has a long history in the mobile business, having been one of the original providers of mobile phone services with the Cellnet joint venture in the UK in the 1980s.
Müller says: "Android already had more than enough intellectual problems anyway. Now Google faces one more large organisation that believes its rights are infringed. BT probably wants to continue to be able to do business with all mobile device makers and therefore decided to sue Google itself."
Google is fending off multiple lawsuits relating to Android, while a number of handset makers including HTC and Samsung have yielded to patent claims by Microsoft against Android and are paying a per-handset fee for every one they make.
Many of the alleged infringements made by Android would also seem to apply to Apple's iPhone and iPad mobile devices – such as the "Busuioc Patent", which detects whether a mobile device is connected to a cellular or Wi-Fi network and allows streaming dependent on that.
Apple's iTunes Match service, launched in the US earlier this year and last Friday in the UK, also detects what sort of connection the device has before allowing file uploads or downloads. It is not known whether Apple has licensed use of the systems from BT, or whether BT has decided they do not infringe its patents, or whether litigation is pending.
BT points in the lawsuit to its large patent portfolio, from research at its Adastral Park centre near Ipswich, and that it has a portfolio of more than 10,000 patents.
The new lawsuit marks a return to attempts by BT to monetise its patent portfolio over web use.
In 2000 it asserted a patent claim in the US against Prodigy, one of the biggest internet service providers, claiming a patent on the hyperlink – the method by which people follow links between pages on the web. But embarrassingly for BT the claim was rejected when a judge said that no jury could find that the patent was infringed.