NEW YORK -- Baseball umpires angry with the computer system used to track their calls behind the plate filed unfair labor practice charges against owners Monday with the National Labor Relations Board.

In a 21-page letter sent to the NLRB's regional office in New York, the World Umpires Association accused management of violating the labor law by refusing to provide information about the computer system, which umpires claim is inaccurate.

"The office of the commissioner has shielded the Questec system from inspection, and from critical inspection by experts trained in the physics of baseball and engineering,'' union lawyer Joel Smith wrote to Celeste Mattina, the NLRB's New York regional director.

"This charge is about a refusal to provide information, about the commissioner's strained efforts to insulate the umpire information system from independent scrutiny, and about the threats uttered by the office of the commissioner in that effort.''

Smith claimed management had "stalled, stonewalled and stymied,'' and said the commissioner's office illegally obstructed the WUA's right to information, failed to supply information, illegally limited access of union lawyers to meet with umpires at ballparks and refused to discuss Questec with union lawyers. He also said the commissioner's office illegally threatened and discriminated against the union and its officers.

Management spokesman Pat Courtney said none of the labor lawyers in the commissioner's office were available for comment. In the past, management lawyer Rob Manfred said his side would discuss the system with umpires only after the season because the union had agreed before the season to allow the system to be used as a "training tool.''

During a summer of escalating anger among umpires over the Questec system, the union has filed a grievance against management, and owners have sued.

The next step is for the NLRB office to decide whether to issue a complaint. If it does, the matter would go before an administrative law judge.