The social services arm of the Roman Catholic archdiocese, which has provided adoption services for the state for about two decades, said the law runs counter to church teachings on homosexuality.
"The world was very different when Charities began this ministry at the threshold of the twentieth-century," the Rev. J. Bryan Hehir, president of Catholic Charities, said in a joint statement with trustees chairman Jeffrey Kaneb. "The world changed often and we adapted the ministry to meet changing times and needs. At all times we sought to place the welfare of children at the heart of our work.
"But now, we have encountered a dilemma we cannot resolve," they said.
Governor Mitt Romney said he planned to file a bill that would allow religious organizations to seek an exemption from the state's anti-discrimination laws to provide adoption services.
"This is a sad day for neglected and abandoned children," Romney said in a statement. "It's a mistake for our laws to put the rights of adults over the needs of children."
The state's four Catholic bishops said earlier this month that the law threatens the church's religious freedom by forcing it to do something it considers immoral.
Eight members of Catholic Charities board of the bishops' stance. The 42-member board had voted unanimously in December to continue considering gay households for adoptions.
Geri Denterlein, one of the board members who resigned, said earlier this month that she supports gay marriage, but her resignation wasn't meant as a political statement. She pointed to a unanimous vote by the 42-member board in December to continue placing children in gay households. The bishops' decision undermines Catholic Charities and eliminates same-sex couples from consideration, even if they're the best choice, Denterlein said.
"I simply didn't feel I could continue to serve as board member when we were at such odds with the way the hierarchy was approaching adoption policy," she said.
Besides Denterlein, president of Denterlein Worldwide Public Affairs, the statement was signed by Donna Gittens, chief executive officer, causemedia; Paul LaCamera, general manager, the WBUR group; Brian Leary, partner, Gadsby Hannah; Peter Meade, executive vice president, Blue Cross Blue Shield of Massachusetts; Colette Phillips, president and CEO, Colette Phillips Communications; Micho Spring, chairman, Weber Shandwick New England.
Catholic Charities has been involved in adoptions for about a century, but has had a contract with the state for the past two decades. Its contract with the state expires June 30.
In that time, Catholic Charities has placed 720 children in adoptive homes, including 13 who were placed with same-sex couples, Catholic Charities said.
In a 2003 document, the Vatican said gay adoption was "gravely immoral," and that children placed in such homes "would be deprived of the experience of either fatherhood or motherhood."
Some 682 foster children are waiting for adoption in Massachusetts, according to the state Department of Social Services. The bulk of adoptive children are placed by DSS, rather than outside agencies such as Catholic Charities, the agency said.