Assuming you work for a private sector employer:
If a union employee wants to pursue a claim against the union, there is a six month time limit, called a statute of limitation, in which to file a lawsuit in federal court claiming a violation of 29 U.S.C. section 301 or file an unfair labor practice charge with a federal agency, the National Labor Relations Board. There is a high hurdle for successful claims against unions. A union must have acted arbitrarily, discriminatorily or in bad faith – far beyond negligence. These cases are very difficult to win, but if the facts are as you describe, you may be able to move forward.
One of the best sources for information about unions and their relationships with the workers they represent is the Association for Union Democracy (AUD) . You may want to visit the AUD website and see if there is anything helpful there.
Public sector union employees have similar rights, per state law.
twitter.com/MikaSpencer *** All legal actions have time limits, called statutes of limitation. If you miss the deadline for filing your claim, you will lose the opportunity to pursue your case. Please consult with an experienced employment attorney as soon as possible to better preserve your rights. *** Marilynn Mika Spencer provides information on Avvo as a service to the public, primarily when general information may be of assistance. Avvo is not an appropriate forum for an in-depth response or a detailed analysis. These comments are for information only and should not be considered legal advice. Legal advice must pertain to specific, detailed facts. No attorney-client relationship is created based on this information exchange. *** Marilynn Mika Spencer is licensed to practice law before all state and federal courts in California, and can appear before administrative agencies throughout the country. She is eligible to represent clients in other states on a pro hac vice basis. ***