Two insiders at the International Brotherhood of Teamsters have signed affidavits claiming their union was involved in fraud by submitting forged signatures to a federal agency in an attempt to raid members from another union.

The insiders also claimed that top officials tried to kept the information quiet and retaliated against people in the union who raised concerns.

In a letter Monday, the Teamsters requested that the agency turn over the whistleblowers’ names.

The Transportation Workers Union first made the  fraud accusations in documents filed with the National Mediation Board on July 16. The board oversees labor issues in the transportation industry.

TWU accused the Teamsters of engaging in the fraud in attempt to convince the board to hold a vote over which union would represent 12,000 American Airlines workers in Tulsa, Oklahoma. TWU currently represents the workers.

The two unions have been locked in a bitter struggle over the Tulsa workers since American Airlines filed for bankruptcy last year. The airline extracted concessions from TWU in August 2012.

To back up its claim, TWU presented two sworn affidavits from Teamster organizers.  The whistleblowers claim that an internal IBT investigation found that at least 1,500 cards supposedly signed by TWU members who wished to join IBT were fraudulent.

“In addition to the Teamster organizers who have come forward we have had a number of staff in the IBT headquarters and in the field validate the evidence,” Frank McCann, TWU’s director of organizing, told the Washington Examiner in an email. “People have been very forthcoming, but some Teamster employees are afraid of retaliation if they go public.”

In a letter to NMB Monday, the Teamsters said they took TWU’s charges “very seriously” and plan to submit a complete response. The union said in its Monday letter to NMB.

The letter also requested that NMB turn over “unredacted versions” of the whistleblowers affidavits so the union could prepare its response.

If proven, the forgery allegations could damage Big Labor’s push for so-called “card check” legislation to change union organizing rules.

Card check would eliminate an employer’s right to request a federally monitored secret ballot election during organizing drives. Instead, the process would only involve unions obtaining worker signatures.

The TWU-Teamster case could show that that method is susceptible to fraud.

McCann nevertheless called the forgeries “very unusual” and said that most union organizers are “hard-working, dedicated people.”

On May 27, the Teamsters filed a request with the NMB to hold a representation election.  They submitted an undisclosed number of signatures from TWU workers who said they wanted new representation. 51 percent are needed to hold a vote.

The documents in the case were provided to the Washington Examiner by TWU. The whistleblowers’ names were redacted.

TWU officials say the two came to them with the allegations. Both affidavits say they came forward “because workers depend on a fair process.”

The whistleblowers do not claim to have personally witnessed any fraud but say top officials inside the IBT’s organizing offices knew of it.

According to one, the internal investigation found “multiple cards from the same workers with different signatures (and) assessments of workers who were never spoken to.”

The second whistleblower said one organizer “was not doing routine home visits to American Airline workers he was assigned to visit, but instead sat in his car and filled out call sheets and falsely signed authorization cards.”

The insider further claims that “IBT senior management was aware of the forgery issue” but that a Teamster official who raised alarms was instead reassigned.

Submitting forged signatures is a potential criminal offense.

David Bourne, director of the IBT’s airline division, told the website on July 24 TWU’s charges were “a diversionary scheme to bring the Teamsters into public disrepute.”

Teamster spokesman Galen Munroe declined the Examiner’s request for a comment.

The NMB is still investigating the Teamster’s request for a vote. It is not clear when it may make a decision.

TWU maintains that the Teamsters are trying to take advantage of discontent caused the airline’s financial woes to “raid” it of its members.

“The IBT is behaving like a parasite,” Garry Drummond, TWU air transport division director, said in a May statement.

The Teamsters are also trying to invalidate 1,300 names on the potential voter list, claiming they are ineligible. TWU contests that claim.

The Teamsters are notorious within organized labor for the “raiding” tactics alleged by TWU. The union split from the AFL-CIO, which bars such activity, in 2005, to join the rival Change To Win coalition.

Since 1992, the union has been operating under strict federal oversight to root out corruption.