Published: Aug 11, 2010 9:39 PM EDT
Updated: Aug 11, 2010 6:39 PM EDT

NEW YORK TIMES - About 340,000 of the 4.3 million babies born in the United States in 2008 — or 8 percent — had at least one parent who was an illegal immigrant, according to a study published Wednesday by the Pew Hispanic Center, a nonpartisan research group in Washington.

Because they were born in this country, the babies of illegal immigrants are United States citizens. In all in 2008, four million children who were American citizens had at least one parent who was in the country illegally, the Pew study found.

Children of illegal immigrants make up 7 percent of all people in the country younger than 18 years old, according to the study, which is based on March 2009 census figures, the most recent data on immigrant families. Nearly four out of five of those children — 79 percent — are American citizens because they were born here.

About 85 percent of the parents who are illegal immigrants are Hispanic, the Pew Center reported.

The Pew study comes as lawmakers in Washington have been debating whether to consider changing the 14th Amendment of the Constitution, which grants citizenship to anyone born in the United States. The controversy erupted after Senator Lindsey Graham, Republican of South Carolina, said in July that he might offer an amendment to revoke birthright citizenship for the American-born children of illegal immigrants.

Mr. Graham’s comments touched a nerve with many Americans, who called in to talk shows to question whether the children of immigrants who have violated the law by remaining in the United States should be granted citizenship. But it was less clear that there was strong support for altering the Constitution to address the problem.

A nationwide survey in June by the Pew Research Center for the People and the Press, a group affiliated with the Hispanic Center, found that 56 percent of those polled opposed changing the 14th Amendment, while 41 percent supported it.

The study by the Pew Hispanic Center casts light on an issue raised by Mr. Graham that prompted the current debate. In an interview with Fox News last month, Mr. Graham said that many illegal immigrants were crossing the border to have babies in this country to gain citizenship for their children. “They come here to drop a child,” Mr. Graham said.

The Pew figures showed that over 80 percent of mothers in the country illegally had been here for more than a year, and that more than half had been in the country for five years or more, said Jeffrey S. Passel, senior demographer at the Pew Hispanic Center and the co-author of the study, along with Paul Taylor, the center’s director.

“The combination of the growing undocumented population through 2007, with more staying in the country longer, creates a situation where we have seen increasing numbers of these births over the last six or seven years,” Mr. Passel said. “Because the immigrants are staying here, this is a young population, and they get married and form families.”

Republican leaders and conservatives have been divided over Mr. Graham’s proposal for a constitutional amendment.

“What the Pew estimate underlines is that this is a big problem,” said Mark Krikorian, executive director of the Center for Immigration Studies, a research group in Washington that advocates reduced immigration. “It really is a subversion of national independence for people who break into your country then to demand that their kids be U.S. citizens.”

But Mr. Krikorian, a conservative, does not favor an immediate effort to amend the citizenship clause of the Constitution. He said he wants to see tougher enforcement to reduce the number of illegal immigrants in the country.

“The point is to shrink the illegal population and prevent new illegals from coming in,” he said, “before it’s appropriate to have the constitutional debate.”