HTC’s battle with Apple continues to rage, with the Taiwanese smartphone maker ignoring complaints it is currently under investigation for and issuing its own in the UK courts.

On Wednesday, HTC said that it filed an “invalidation action” against Apple in a UK court, a method of challenging the validity of a patent if the patent holder didn’t invent the product under investigation, or hasn’t disclosed enough information about what the patent covers or how it has been infringed.

HTC is currently under investigation in the US after the US International Trade Commission ruled that it had infringed on two Apple patents, a judgement that HTC has said it will appeal. Apple seeks the blocking of HTC smartphone imports as they infringe on patents related to the implementation of operating systems.

The Taiwanese smartphone vendor has not elaborated on the details of the case, stating:

We don’t comment on pending litigation. As a leading smartphone innovator, we respect intellectual property of others and will defend our own intellectual property as needed.

More information is expected to become available if – or when – Apple acknowledges the lawsuit in the UK.