Microsoft’s patent spat with InterDigital moved up a notch, with the computing giant alleging that the licensing firm failed to keep a promise on the terms under which it offers access to essential technology.

According to Bloomberg, Microsoft said that InterDigital had gone back on a pledge to licence patents deemed essential to a standard at the reasonable rates normally associated with such intellectual property.

Having had its technology accepted as essential, InterDigital began charging “exorbitant licence rates”, the complainant said in a statement.

Microsoft made its latest assertions in a case filed in a US federal court.

The two companies are involved in a US International Trade Commission (ITC) case which began in 2007, filed when Microsoft’s Devices business was still owned by Nokia.

Earlier this year, InterDigital issued a triumphant statement following an initial determination from the ITC, which said that it “prevailed in its complaint” against Nokia and Microsoft.

InterDigital has sought the prohibition of import into the US devices made by Microsoft which include 3G technology which are alleged to infringe two of its patents, although CIO said that InterDigital had asserted it is looking for a deal, rather than a bar.

In April, InterDigital said a final ruling from the ITC is “currently expected by 28 August 2015”.