Qualcomm made the accusations in a motion to amend a complaint filed in November, when it alleged Apple had broken a software license contract by sharing confidential details about Qualcomm's chips with Intel engineers.
Qualcomm provided modem chips for the iPhone, which helped the device connect to wireless data networks. Starting with the iPhone 7, however, Apple began using Intel modem chips in some of its models.
Tuesday's allegations were made in a planned legal filing seen by Reuters.
They go further than the original complaint by alleging Apple stole Qualcomm trade secrets in a "multi-year campaign of sloppy, inappropriate and deceitful conduct ... for the purpose of improving lower-quality modem chipsets, including those manufactured by Intel, a competitor of Qualcomm, to render such chipsets useable in Apple devices with the ultimate goal of diverting Qualcomm's Apple-based business to Intel."
Qualcomm previously informed investors that its modem chips have been removed from Apple's product roadmap.
