Microsoft has revealed this week that sat-nav firm TomTom is counter-suing the Redmond company for an alleged patent breach.

In February it was revealed that Microsoft was suing the sat-nav developer over patents relating to its navigation technology. Now TomTom has launched its own legal action, claiming that Microsoft's Streets and Trips program infringes on four of its patents.

Streets and Trips is Microsoft's mapping, GPS and directions software application. TomTom is asking for damages for wilful infringement, because it claims to have previously notified Microsoft about the program's alleged infringement.

Microsoft had previously claimed that TomTom infringed on eight of its patents. In a statement released late Thursday, Horacio Gutierrez, corporate vice president and deputy general counsel of Intellectual Property and Licensing at Microsoft, said that despite the TomTom counter-claim, its plans would not change.

"We are reviewing TomTom's filing, which we have just received. As has been the case for more than a year, we remain committed to a licensing solution, although we will continue to press ahead with the complaints we initiated in the US District Court for the Western District of Washington and the International Trade Commission."