Apple has accused regulators in the US of running a "smear campaign" against it in the legal fight over unlocking iPhones.
In its latest court filing, the Department for Justice (DoJ) said Apple's refusal to cooperate with its demands was "corrosive" of the organisations and institutions that protect "liberty and rights".
The DoJ also claims that Apple assisted the Chinese government with security matters last year. It claims the Chinese government made 4,000 requests for information regarding iPhones, which were accepted by Apple in 74% of cases.
Apple's general counsel Bruce Sewell said the DoJ's brief "reads like an indictment".
He said: "Everybody should beware because it seems like disagreeing with the Department of Justice means you must be evil and anti-American, nothing could be further from the truth."
The DoJ has accused Apple of describing the FBI's investigation as "shoddy", while positioning itself as a "guardian of Americans' privacy".
It said: "[The] rhetoric is not only false, but also corrosive of the very institutions that are best able to safeguard our liberty and our rights: the courts, the Fourth Amendment, longstanding precedent and venerable laws, and the democratically elected branches of government."
Apple hit back saying: "This case is about the Department of Justice and the FBI seeking through the courts a dangerous power that Congress and the American people have withheld."
In February, Apple received a court order demanding it assisted the FBI in unlock the iPhone of Syed Rizwan Farook, the terrorist who killed 14 people and injured 22 others in California in December. Apple soon rejected the demand, claiming it would "undermine decades of security advancements that protect our customers".
Since then, some of the world's biggest tech firms have supported Apple in its stance, filing an amicus brief - a document which gives those not involved in a case, but that may be affected by the outcome, a say.