A U.S. senator has told Activision Blizzard CEO Bobby Kotick to "negotiate in good faith" with Raven Software employees attempting to unionize.

As reported by The Washington Post, Sen. Tammy Baldwin expressed concern at recent media reports that indicate Activision Blizzard has been employing union busting tactics to frustrate Raven workers, and told Kotick to "suspend any efforts to undermine your employees' legal right to form a union and collectively bargain."

Raven QA workers and Activision Blizzard are currently participating in a National Labor Review Board (NLRB) hearing that aims to define which employees can be included in the QA unit, and notably who can vote for or against the union. 

Union representatives, however, have claimed that Activision Blizzard is trying to "thwart" their bid to organize under the Game Workers Alliance banner by reorganizing the QA department and embedding staff into different teams across the company, effectively dividing pro-union workers and potentially diluting the vote.

Senator Baldwin described those reports as "troubling" and is pushing Kotick to remain neutral in the NLRB election.

"I understand the National Labor Relations Board is currently considering the appropriate bargaining unit for a potential election. I am troubled by reports that describe significant changes to the organizational chart at Raven -- announced by management shortly after the union drive began," reads the letter.

"These changes scatter quality assurance testers throughout the company, embedding them in inappropriate departments (such as marketing) possibly in an attempt to frustrate efforts by the testers to form a bargaining unit comprised only of quality assurance testers. I will be following the proceedings at the National Labor Relations Board and Raven Software closely."

Baldwin also sent a copy of the letter to Microsoft CEO Satya Nadella, with the software company and Xbox maker currently in the process of purchasing Activision Blizzard for $68.7 billion. 

Those interested can see the letter in full on The Washington Post.