The bishop of Brooklyn, Nicholas DiMarzio, doesn’t mince words.

“I grew up in Newark, New Jersey. Not exactly the most sophisticated place in the world. We called a spade a spade,” the bishop said. “That’s it. That’s my history. I can’t change it.”

These days, Brooklyn’s leading Catholic cleric is talking about the need for tax credits to help parents offset the costs of tuition at private and parochial schools. The proposal faces resistance from politicians and union leaders who say the aid would signal an abandonment of struggling city public schools.

Now in his third year leading a diocese that serves 1.8 million people in Brooklyn and Queens, Bishop DiMarzio, 61, has assumed a leading role in pushing for tuition tax credits at the state and national levels. A week ago he stood with Rep. Vito Fossella in Brooklyn to endorse the Republican congressman’s bill to give a $4,500 tuition tax credit to parents of students in private and parochial schools nationwide.

In an interview last week as he sat in a conference room on the seventh floor of the diocese’s Greene Avenue headquarters, Bishop DiMarzio said the argument that education tax credits would hurt public schools makes little sense. On the contrary, he said, the aid would help non-public schools and taxpayers alike.

“The more children that are in nonpublic schools, the taxpayer saves money, if you want to look at it just from a purely economic view,” Bishop Di-Marzio said.

The bishop takes a broader perspective, seeing tax credits as offering the freedom of choice for parents and fostering a healthy competition among public, private, and parochial schools. He argues for the need to combat the monopoly that, in his view, exists now for public education.

“I think our country’s been against monopolies for a long time,” Bishop Di-Marzio said. “Look at your history books. Now we have an educational monopoly in the public education that I think is detrimental, because there’s no competition. If there’s no competition, it’s very difficult to improve. There’s nothing to compare to.”

The influential state and city teachers’ unions have thrown their lobbying weight against education tax credits. A spokesman for the New York State United Teachers, Dennis Tompkins, said a comparison between public and private education was inappropriate, because unlike city schools, parochial academies could choose what students to take. Mr. Tompkins cited a recent court ruling that requires the state to spend billions more annually on public schools and said that to divert funds to private and parochial causes before that money is paid out “seems sort of unfair.” Governor Pataki is appealing the case, and this year the state allocated $11.2 billion in capital money for New York City schools.

True to his nature, Bishop DiMarzio has been outspoken in his push for tuition tax credits. When the state Assembly speaker, Sheldon Silver, suggested in late March that parochial schools leaders would respond to Governor Pataki’s proposed $500 tax credit by raising tuition the same amount, Bishop DiMarzio fired off a letter to state lawmakers. The bishop wrote that he took “personal umbrage” at Mr. Silver’s remarks, which he said contradicted a pledge that he and other religious leaders had made in a meeting with the speaker weeks earlier. “It is tragic that the leader of the Assembly whom you elected would misrepresent the intentions of religious leaders in our state!” Bishop DiMarzio wrote.

The bishop’s aggressiveness is well known to those who work with him regularly. “He’s a tough guy, in the best sense,”the executive director of the New York State Catholic Conference, Richard Barnes, said. “He’s willing to ruffle feathers in pursuit of his objectives.”

The head of the Catholic Charities of Brooklyn and Queens, Robert Siebel, said he found the bishop both “exciting and challenging” to work with. “He really wants the best, and he won’t settle for less,” he said.

Associates of Bishop DiMarzio say his rough edges are tempered by an uncommon warmth and an “infectious” laugh. A Brooklyn assemblyman and the chairman of the borough’s Democratic party, Vito Lopez, said that when he fell ill and needed heart surgery in March, Bishop DiMarzio called him and invited him to a private Mass for his family at the bishop’s home in Fort Greene. “It was very humbling and something I’ll never forget,” Mr. Lopez said.

To build a coalition to fight for education tax credits, Bishop DiMarzio reached across religious lines, working closely with the Sephardic Community Federation. The group’s executive director, David Greenfield, said that at a dinner in March between Catholic and Jewish leaders at Prime Grill, a kosher steakhouse in Manhattan, the bishop pointedly chose a non-denominational prayer to recite before the meal. “It’s the kind of thing he would do to reach out to the Jewish community,” Mr. Greenfield said.

The bishop’s stepped-up advocacy also has the backing of the archbishop of New York, Cardinal Edward Egan, who has been equally vocal in his support for tax credits in recent months. Along with Bishop DiMarzio, Cardinal Egan led thousands at an Albany rally in February. In April, the cardinal penned a letter to Mr. Fossella thanking him for his proposal. Speaking through his spokesman, Joseph Zwilling, Cardinal Egan said he was “very pleased that both bishops who represent New York City are speaking with one mind on this issue.”

The campaign for education tax credits comes at a time when Catholic schools in the New York area are struggling to keep up with rising costs and shifts in population that have resulted in declining enrollment. In what he called the most difficult decision of his tenure, Bishop DiMarzio in 2005 closed 20 schools as part of a consolidation of the parish. Six more are slated to close or merge after this year, the diocese announced last month. “A lot of people felt hurt by it. They don’t understand it,” the bishop acknowledged, but he added: “I don’t regret it. It was the right decision. It was the only one that could be made. There wasn’t any alternative.”

The issues of tax credits and school closings go hand in hand, Bishop DiMarzio said. “They’re related in the sense that if people can afford tuition, people will come to our schools,” he said. “If they can’t afford it, they stay away. When we don’t have students, we have to close schools.”

While Bishop DiMarzio has focused on education in recent months, the issue he has devoted the most attention to over his 36-year career as a priest is immigration. After attending Catholic schools as a youth, he was ordained in his hometown of Newark, and later served as bishop of Camden, N.J., before assuming the helm of the Brooklyn diocese in August 2003. He has held chairmanships of the Catholic Legal Immigration Network and of the migration committee of the U.S. Conference of Catholic Bishops.

The bishop has repeatedly spoken out in defense of the many illegal immigrants in his diocese, and rejects calls for deportation. “People are coming here because there are places to work,” he said. “Do you see the undocumented camped in Central Park, or someplace else, in Prospect Park? In tents? They’re all working, and they’re all living in houses where they pay rent.” He argued that the landlords pay taxes on the rent, so that the immigrants are “paying taxes.”

Bishop DiMarzio’s penchant for speaking his mind has drawn criticism from some, most notably when in 2004 he likened same-sex marriage to the idea of marrying one’s pet. The bishop says he was misinterpreted and that he was simply using the logical mechanism of “reductio ad absurdum,” or reducing something to the absurd.

Asked if he’s ever been told to tone down his outspoken style, the bishop laughed. “They may have said that,” he said. “I didn’t pay much attention, unfortunately.”

Whether it’s about education, immigration, or social issues, Bishop DiMarzio has no plans to quiet down. “That’s my style,” he says, “and I’m not about to change it, and I see no reason to change it.”