Hyatt Hotels Corp. faced the wrath of religious leaders Tuesday as hotel workers called for a boycott of three Hyatt branded Chicago hotels.

“I think it is immoral. It’s immoral. It’s immoral for Hyatt to be treating its workers the way they are treating them: A year without a contract,” Rev. Calvin Morris boomed into a microphone outside Hyatt’s downtown headquarters. “We’re going to boycott these hotels, and we do so with good conscience.”

The world’s largest group of Jewish Clergy, the Central Conference of American Rabbis, has pledged its support for the worker-led boycotts, which with the addition Tuesday of Hyatt Regency Chicago, Hyatt O’Hare and Park Hyatt in Chicago, now number 10 at Hyatt properties across the country. Approximately 250 rabbis, cantors and other Jewish leaders have also signed a pledge in support of the boycotts.

Contracts for 6,000 hotel workers in Chicago expired a year ago, and labor negotiations have been unsuccessful. While the contracts affect workers at several hotel chains, Unite Here has focused on Chicago-based Hyatt and the Pritzker family, which controls the chain, holding them up as an example of management using the economy as an excuse to take advantage of workers.

John Schafer, vice president and managing director for Hyatt Hotels & Resorts, said Hyatt has been honoring the terms of the expired contract and said a boycott only serves to threaten the city’s economic recovery, including jobs.

“Union leadership clearly prefers to focus its energy on tactics intended to grow its membership rather than working to achieve a fair contract,” he said, citing a two-month delay in negotiations.

Schafer said the proposal Hyatt has brought forward could include employee contributions but that nothing is off the table yet. Full-time workers “have some of the industry’s best wages and benefits,” Schafer said, making $15 to $30 an hour, with no-cost pension, no-cost health care, holiday pay, paid vacation, paid sick days and other benefits.

“We’re trying to work with the union and figure out…how can we work together to control healthcare costs?” he said.

Workers said the proposals would increase their out-of-pocket health care costs.

Gabriel Carasquillo said Hyatt’s good health care package is one of the reasons he signed on to be a server at Park Hyatt, but the changes, he said, would double his health care costs to about $6,400 a year.

“I truly believe that my health should not be a point of negotiation,” he said.

Carmen Sandoval, a room attendant at the Hyatt Regency O’Hare for 30 years, said her husband’s laundry department was laid off without warning, and he cannot find a job. She said Hyatt recently brought in temporary workers that would perform their jobs in their absence; a tactic she said was intimidating. Hyatt hotel workers recently voted to authorize a strike if necessary.

Schafer said the hotel chain is preparing in case a strike occurs.

“Obviously, a strike vote has been taken against the Hyatts of Chicago, and our druthers would be for all of our workers to show up every day and do a good job taking care of our guests…If they don’t, we have to continue to operate the business,” he said.

Rabbis and reverends alike broke off into two groups after the event to tell downtown businesses that have booked events at the Chicago Hyatt properties about the boycott. Unite Here said it plans to send letters about the boycotts to other organizations that have booked events at the Hyatt properties. A similar tactic, used by the union last November, led the Chicago Convention and Tourism Bureau to protest the union letters as “harassing” and harmful to tourism in Chicago.

“No celebration can be truly joyous if it takes place at an institution that withholds wages from its most vulnerable employees,” said Rabbi Alison Abrams of Long Grove, who signed a pledge in support of the boycotts.

Union-led boycotts in Boston prompted Emerson College to pull three events from Hyatt hotels, including a holiday party. Suffolk University stopped using the Hyatt Regency Boston for student housing, and Hyatt properties lost the business of several conferences and events, including the National Organization of Women 2010 conference, the Eastern Sociological Society 2010 conference, NAACP Martin Luther King Breakfast and a conference for Jewish Chaplains, according to Unite Here.

In a statement, Robb Webb, chief human resources officer for Hyatt Hotels, called the union’s efforts with religious leaders part of a “misinformation campaign.” The union, he said, has been attempting to remove a secret-ballot process for choosing union representation as a way to expand membership.

In December, more than more than 200 rabbis and cantors across the country signed a petition calling on Hyatt to rehire 98 Boston housekeepers who were let go and replaced with cheaper, outsourced labor in August 2009. At its first public shareholders meeting this June, the company faced dozens of religious leaders who compared Hyatt’s labor practices with Pharaoh’s enslavement of the Israelites.

“Clearly, leadership for the Central Council of American Rabbis has been misinformed by the union, and we are disappointed that CCA has chosen to take a position without asking for the facts or giving Hyatt the opportunity to present our point of view regarding how we are working to provide associates with a fair contract and a great place to work,” Webb said.