Your question has a lot of important factual issues balled up in it. Who and what constitutes this "group"? Why is your employer implicated -- is it a group at work? What kind of office or shop do you work in? Are you a union member? Are you in management? Is the speaker in management and senior to you? Has your career been affected by these statements?
It appears that it makes sense for you to find a lawyer with experience both in employment law and defamation law to listen to the full scope of your situation and advise you appropriately. Good luck.