WASHINGTON >> In a major policy reversal, the Obama administration said Wednesday it will no longer defend the constitutionality of a federal law banning recognition of same-sex marriage.

Attorney General Eric Holder said President Barack Obama has concluded that the administration cannot defend the federal law that defines marriage as only between a man and a woman. He noted that the congressional debate during passage of the Defense of Marriage Act “contains numerous expressions reflecting moral disapproval of gays and lesbians and their intimate and family relationships — precisely the kind of stereotype-based thinking and animus” the Constitution is designed to guard against. 

The Justice Department had defended the act in court until now.

The move quickly drew praise from some Democrats in Congress but a sharp response from the spokesman for Republican John Boehner, the House Speaker.

“While Americans want Washington to focus on creating jobs and cutting spending, the president will have to explain why he thinks now is the appropriate time to stir up a controversial issue that sharply divides the nation,” said Boehner’s spokesman Michael Steel.

Gay groups, which had long pressured the administration to take a step like this, were pleased. Ron Carey, executive director of the National Gay and Lesbian Task Force, called the policy change “a tremendous step toward recognizing our common humanity and ending an egregious injustice against thousands of loving, committed couples who simply want the protections, rights and responsibilities afforded other married couples. We thank the Obama administration.”

Obama’s move may position him politically at the forefront of rising public support for gay marriage. Polling results can vary rather significantly depending on what words are used to describe gay marriage, but there is a gradual trend in public opinion toward more acceptance of gay marriage. 

An Associated Press-National Constitution Center Poll conducted last August found 52 percent of Americans saying the federal government should give legal recognition to marriages between couples of the same sex, while 46 percent said it should not. In polling by ABC News and the Washington Post, support for the legalization of gay marriage has climbed from 37 percent in 2003 to 47 percent in February 2010. 

Holder’s statement said, “Much of the legal landscape has changed in the 15 years since Congress passed” the Defense of Marriage Act. He noted that the Supreme Court has ruled that laws criminalizing homosexual conduct are unconstitutional and that Congress has repealed the military’s “don’t ask, don’t tell” policy.

At the White House, spokesman Jay Carney said Obama himself is still “grappling” with his personal view of gay marriage but has always personally opposed the Defense of Marriage Act as “unnecessary and unfair.”

Holder wrote to Boehner that Obama has concluded the Defense of Marriage Act fails to meet a rigorous standard under which courts view with suspicion any laws targeting minority groups who have suffered a history of discrimination.

The attorney general said the Justice Department had defended the law in court until now because the government was able to advance reasonable arguments for the law based on a less strict standard.

At a December news conference, in response to a reporters’ question, Obama revealed that his position on gay marriage is “constantly evolving.” He has opposed such marriages and supported instead civil unions for gay and lesbian couples. The president said such civil unions are his baseline — at this point, as he put it.

“This is something that we’re going to continue to debate, and I personally am going to continue to wrestle with going forward,” he said.

On Wednesday, Holder said the president has concluded that, given a documented history of discrimination against gays, classifications based on sexual orientation should be subject to a more heightened standard of scrutiny than the department had been applying in legal challenges to the act up to now.

The attorney general said the department will immediately bring the policy change to the attention of two federal courts now hearing separate lawsuits targeting the Defense of Marriage Act.

One case, in Connecticut, challenges the federal government’s denial of marriage-related protections for federal Family Medical Leave Act benefits, federal laws for private pension plans and federal laws concerning state pension plans. In the other case in New York City, the federal government refused to recognize the marriage of two women and taxed the inheritance that one of the women left to the other as though the two were strangers. Under federal tax law, a spouse who dies can leave her assets, including the family home, to the other spouse without incurring estate taxes.