Google has begun legal proceedings against BT in a Californian court over four patents as it vowed to defend itself against "patent trolls".
BT had issued its own legal action against Google in 2011 over six patents relating to mobile technology but is now facing new action from the search giant.
In a statement sent to V3, Google said it was only taking the action "as a last resort" and had no other option given BT's aggressive stance.
"BT has brought several meritless patent claims against Google and our customers - and they've also been arming patent trolls," it said.
"When faced with these kind of actions, we will defend ourselves."
V3 contacted BT for comment on the developments but it said it does not comment on pending litigation.
The case represents just another in the long of patent cases dominating the technology landscape, involving the likes of Google, Apple and Samsung, with cases grabbing the headlines around the world throughout 2012.
Since the turn of the year these cases have showed no signs of easing, with Apple attempting to have its initial $1bn court win against Samsung increased to $3bn, although this was rejected by a US judge.