The Communications Workers of America (CWA) union has pressed charges against publishing giant Activision Blizzard over allegations staff were fired for using "strong language" in opposing a return to the office.

As reported by Kotaku, the Call of Duty maker has apparently fired two members of staff from its quality assurance department after they expressed outrage at the mandate to return to the office to work. The exact charges that the CWA is pressing have not been publicly disclosed, but they have been directed at CEO Bobby Kotick.

The two members of staff in question were apparently fired for using "strong language", after which they had disciplinary meetings and were subsequently fired.

"For far too long, Activision has gotten away with treating its employees, especially QA testers, like disposable workhorses," the CWA's secretary-treasurer Sara Steffens said.

"Firing two employees for joining with their co-workers to express concern around hasty return to office policies is retaliation, point blank.

"When faced with unfair treatment by unscrupulous employers like Activision, workers should have the right to express themselves."

The CWA has claimed that the use of "strong language" in this instance had previously been protected by the National Labor Relations Board (NLRB). Changes made under the Trump administration eroded this protection, meaning that staff can be fired for strong language.

In its own statement, Activision Blizzard's Joseph Christinat said that the two staff members were fired for their language. 

"We don’t allow employees to use profane or abusive language against each other," he said.

"We’re disappointed the CWA advocates this type of behaviour.”