Starbucks is asking the federal labor board to suspend all mail-in ballot union elections nationwide, alleging misconduct in the voting process by the board’s personnel and the union organizing its baristas.

The Seattle-based coffee giant wrote in a letter to the chairman and general counsel of the National Labor Relations Board on Monday that the labor board’s officials acted inappropriately during an election in the Kansas City area and has likely acted similarly in other elections. Starbucks cited a career NLRB professional who approached the company as a whistleblower.

More than 220 Starbucks cafes in the U.S. have voted to unionize, according to an NLRB tally as of Friday. An additional 34 elections have been ordered or are in progress, and seven more stores are waiting to schedule elections.

Starbucks Workers United and the NLRB did not immediately respond to requests for comment from CNBC.

In addition to asking for a pause on all scheduled mail-in elections at its U.S. stores, Starbucks is requesting that all future elections be held in person while the allegations can be investigated.

According to Starbucks, NLRB officials allegedly coordinated with union agents to arrange for in-person voting at the labor board’s offices during mail-in ballot elections. The company also alleges that Workers United agents were given confidential, real-time information about specific vote counts so the union could target employees who hadn’t voted yet. NLRB officials and Workers United then allegedly coordinated to cover up this activity, the company said.

Starbucks’ letter details email correspondence that allegedly occurred between union representatives and labor board officials. The company said it was informed of the emails’ contents by the whistleblower.

Starbucks said that similar behavior has occurred in elections in Seattle and Buffalo, New York, as well.

“Until a thorough investigation is conducted it’s anyone’s guess how many elections in how many other regions have been similarly infected,” the company said in the letter.

Under interim CEO Howard Schultz, Starbucks has more aggressively opposed unionization efforts at its locations. So far, the number of unionized cafes is a small portion of Starbucks’ nearly 9,000 company-owned cafes, but the coffee chain has been working to curb the union’s momentum.

For example, Starbucks announced a new round of pay hikes in May for tenured workers but said the changes wouldn’t apply to unionized locations, saying they’d have to go through the bargaining process. Earlier this month, Workers United formally asked the company to extend the pay hikes to those locations.

Starbucks is also facing 284 charges of unfair labor practices from the union, according to the NLRB. Allegations of the company’s misconduct include claims that it illegally fired organizers, shuttered stores or harassed its employees to stop baristas from unionizing. Starbucks has denied all claims of union busting.