JACKSON, Mississippi -- A vote on unionization by dealers at the MGM Gold Strike Casino in Tunica County has been put off amid charges that MGM Resorts International broke federal law while campaigning against union representation.

About 300 workers had been scheduled to vote Saturday on whether the United Auto Workers would represent them.

The Gold Strike has about 1,300 employees, according to filings with the Mississippi Gaming Commission. It has the largest number of hotel rooms and slot machines among the eight Tunica County casinos.

The UAW filed unfair labor practice charges Thursday with the National Labor Relations Board, alleging that casino managers illegally:

-- Used employee tip money to conduct anti-union meetings.

-- Told employees their pay would be cut if they voted for union representation.

-- Interrogated employees as to how they would vote.

-- Told employees ballots would require employee ID numbers and thus wouldn't be secret.

"The Gold Strike casino is using heavy-handed tactics in violation of federal law," UAW regional director Ray Curry said in a statement. "We're asking the National Labor Relations Board to investigate, and we're calling on MGM to respect its employees' rights the same way its casinos do in other markets around the country."

MGM, based in Las Vegas, Nevada, denies wrongdoing.

"We are disappointed that employees will not be able to exercise their right to vote on Saturday in an election, which the National Labor Relations Board has cancelled as a result of the union's charge," MGM spokesman Gordon Absher said in a statement. "We will vigorously defend against this charge, which is without merit."

Officials with the labor board didn't respond to requests for comment Friday.

U.S. Rep. Bennie Thompson, R-Miss., had sent a Jan. 1 letter to workers supporting the unionization drive. Thompson wrote that the dealers at the Gold Strike casino were being treated differently than dealers at other MGM properties around the country and differently than other types of workers at the Tunica casino.

A group of three unions -- UNITE HERE, the International Brotherhood of Teamsters and International Union of Operating Engineers -- organized about 500 food, housekeeping and front desk workers in June when MGM International recognized the unions without an election. Scott Cooper, gaming organizing director for UNITE HERE, said those unions are in contract talks with the company. It's unclear why MGM recognized those unions but not the UAW.

Unlike in some casino centers such as Las Vegas and Atlantic City, New Jersey, most casinos in Mississippi aren't unionized. Unions represent some workers in Tunica County at the Tunica Roadhouse Casino & Hotel and Sam's Town Hotel & Casino, as well as at Harrah's Gulf Coast Casino Hotel & Spa in Biloxi.