A Board of Aldermen hearing on unionization disputes at Yale-New Haven Hospital has been called off after the hospital’s top administrator declined to attend.

In a letter sent to aldermen Wednesday, hospital President and CEO Marna Borgstrom said she would not attend a public hearing on last month’s canceled unionization election until three ongoing investigations have been completed. The reviews could take weeks to complete, and Borgstrom’s announcement marks the latest setback for community members trying to find out what role hospital administrators played in violating an agreement with SEIU District 1199, the union which is currently attempting to organize 1,800 hospital employees.

Borgstrom and members of the hospital Board of Trustees — which includes University President Richard Levin and School of Medicine Dean Robert Alpern — were invited to a meeting of the Board of Aldermen’s Community Development Committee, scheduled for this evening. But with the hospital administration not in attendance, the hearing has been canceled, Board of Aldermen President Carl Goldfield said.

Goldfield, who has been among the most outspoken critics of hospital actions in recent months, expressed disappointment with Borgstrom’s refusal to discuss the matter in a public hearing.

“I think that what’s said about this labor situation should be subject to scrutiny,” Goldfield said.

In her letter, Borgstrom said that discussing possible actions in public would be inappropriate and possibly prejudicial to the different investigations that are still ongoing.

“To appear at a public hearing to discuss ongoing matters not yet ruled upon would be premature and would not provide the public or the Board of Aldermen with the complete background they seek,” she wrote.

Hospital spokesman Vin Petrini said Borgstrom would meet with aldermen once the reviews are completed.

Margaret Kern — a private arbitrator hired to rule on any disputes under the Election Principles Agreement signed by the hospital and union last spring — continues to hold hearings on more than 200 complaints from pro-union employees.

On Dec. 13, she ruled that the hospital violated the agreement by holding mandatory meetings on the union election issue during work time. The decision cleared the way for the union to file a complaint with the National Labor Relations Board, which called a halt to the election shortly thereafter.

As hearings continue, Kern is not expected to rule on the complaints in the near future, SEIU District 1199 organizer Bill Meyerson said. Kern has also heard testimony relating to several hospital complaints against the union, including television commercials aired in early January that criticized the hospital’s actions.

Meyerson said he had no further comment on the complaints lodged against the union.

The NLRB is continuing its own investigation into possible violations of federal labor law in the weeks leading up to the scheduled election. But with hundreds of potential witnesses, their review is not expected to end for at least weeks, if not months.

The hospital Board of Trustees also hired Stan Twardy — a former federal prosecutor and current partner in the law firm Day Pitney — to conduct an internal investigation. Twardy’s review has been underway for several weeks, but there is no time frame for how long it will last, Petrini said.

The investigation is independent of hospital management, according to Borgstrom’s letter, and Twardy said his report will be sent directly to the hospital Board. Twardy declined to comment further on his investigation.

Meanwhile, the Undergraduate Organizing Committee has entered the public debate, asking students to sign a petition calling for card check neutrality that it plans to deliver to Borgstrom and Levin sometime in the near future, UOC member Phoebe Rounds ’07 said.

Under card check neutrality agreements, a union can negotiate on behalf of employees once more than 50 percent of the affected employees sign a union membership card, whereas winning a secret ballot election requires receiving more than half the votes during a time-bound election period — two days in this case. Union and city leaders, including New Haven Mayor John DeStefano Jr., have said that a fair secret ballot election will no longer be possible, and have called for a card check process instead.

Rounds said dozens of Yale students were planning to attend the hearing scheduled for today.