Microsoft has hired an official from the European Commission who was involved in the antitrust case against the software giant.
Detlef Eckert is joining Microsoft to work on its Trustworthy Computing project.
Microsoft has said it is doing nothing wrong in hiring Eckert, as he will not be involved in any lobbying activity.
He will instead be working in a business unit which aims to improve the security of the company's software.
But the Computer and Communications Industry Association (CCIA), whose members include many Microsoft rivals, is reportedly unhappy with Eckert's move.
CCIA president Ed Black said the organisation had held sensitive discussions with the official, according to the Financial Times.
"I wouldn't have said what I said if Microsoft was sitting in the room," he is reported as saying.
The Commission is expected to rule on the Microsoft case within weeks.
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