Google has filed patent infringement suits against BT in the US and UK after the telco "armed patent trolls".

Read this 330Mbps prices to fall as BT cuts fibre-to-the-premises wholesale fees Many businesses should be able to get full-fat fibre connectivity for a lower price as of next year, when BT Openreach will cut its wholesale pricing for FTTP-enabled areas and introduce its FTTP-on-demand option, also at the lower cost. Read More

Google filed a complaint on Wednesday in the US District Court for the Central District of California over BT's alleged infringement of four patents, some of which Google has acquired recently from the likes of IBM and Fujitsu.

Details about Google's complaint against BT in the UK are expected to be available soon. The documents are not thought to be available yet as BT has not officially been served in the UK, ZDNet sister site CNET reported on Wednesday. Google's Motorola Mobility unit is also involved in the suit, according to Reuters.

The move follows BT's complaint against Google in the US District Court of Delaware in December 2011 , which claimed over a dozen Google brands, from search and Google Maps to DoubleClick and Gmail, infringed on six of its patents.

BT's patent actions have forced it to countersue, Google said.

"We have always seen litigation as a last resort, and we work hard to avoid lawsuits. But BT has brought several meritless patent claims against Google and our customers — and they've also been arming patent trolls. When faced with these kind of actions, we will defend ourselves," Google said in a statement.

BT declined to comment on the matter.

"BT has brought several meritless patent claims against Google and our customers — and they've also been arming patent trolls" — Google

The four US patents Google is asserting against BT include Patent Nos. 5,581,703, 5,701,465, 6,801,166 B1 and 7,460,558 B2. Google's US complaint alleges a number of BT's US managed services and other voice products infringe on its patents.

Google's reference to "patent trolls" may be a reference to at least two suits it is caught up with either directly or via Motorola Mobility, over patents formerly held by BT.

Suffolk Technologies filed a complaint Google late last year based on patents BT previously owned, according to Reuters.

Another company, Steelhead Licensing, has used patents formerly held by BT to sue several Android device makers, including Google's Motorola Mobility, as well as Apple, RIM and several US carriers, according to Foss Patents blogger Florian Mueller.