Apple’s ongoing dispute with Qualcomm, which saw the tech giant stop payments to the chip-maker last month, has escalated to the point of Qualcomm suing Apple’s four iPhone and iPad manufacturers.

The latest development has seen the US chip-maker file a complaint in the US District Court of the Southern District of California against the Foxconn Technology Group, Pegatron Corporation, Wistron Corporation, and Compal Electronics. The four manufacturers are accused of breaching their license agreements by refusing to pay Qualcomm for the use of its technologies.

The four manufacturers have said they are refusing to pay royalties by instruction of Apple, however, they continue to pay royalties to Qualcomm for the use of its technologies in non-Apple products. Qualcomm says the agreement between itself and the manufacturers was made before Apple sold its first iPhone, and that it is not a party to any of the agreements.

“It is unfortunate that we must take this action against these long-time licensees to enforce our agreements, but we cannot allow these manufacturers and Apple to use our valuable intellectual property without paying the fair and reasonable royalties to which they have agreed,” said Don Rosenberg, EVP and general counsel of Qualcomm. “As Apple continues to collect billions of dollars from consumer sales of its Qualcomm-enabled products, it is using its market power as the wealthiest company in the world to try to coerce unfair and unreasonable license terms from Qualcomm in its global attack on the company.

“Our license agreements with Apple’s manufacturers remain valid and enforceable. The manufacturers must continue to live up to their obligations under these agreements and Apple should immediately cease its tortious interference.”