PHOENIX - About one out of every 15 children in the United States was born to a family in which at least one parent is in this country illegally, according to a new report issued today.

And 80 percent of those 5.1 million children - including 340,000 born in just 2008 - are citizens because they were born in the United States, the Pew Hispanic Center concluded. According to some, that makes them "anchor babies" for their illegal parents.

The figures, which the organization calculated based on 2009 U.S. Census Bureau estimates, are the best estimates to date of the scope of the issue, which has resulted in calls to amend the U.S. Constitution to deny automatic citizenship to children solely by virtue of their birth in this country.

While no specific language has been crafted, it likely would say citizenship for a newborn depends on at least one parent being a citizen. If that is the language, the number of youngsters affected would be much smaller than in the Pew study.

Jeffrey Passel, Pew senior demographer, said the organization was unable to calculate the number of children who have two illegal-immigrant parents. "Logically, the number with two unauthorized parents would be less than our estimate," he said.

It's unclear what would happen to children with parents who are legal permanent residents or to kids whose parents are in the U.S. legally with temporary visas.

The Immigration Policy Center, an immigrant-rights organization in Washington, D.C., said in a news release that without data on children with two illegal parents, the report "offers no real clarity."

Whether the change would strip citizenship from one baby or 1 million, it's a mean-spirited plan that wouldn't help the country with its illegal-immigration issues, said Michele Waslin, senior policy analyst with the Immigration Policy Center. Waslin also said calling these children "anchor babies" is both offensive and inaccurate.

Pew calculated that the percentage of children of illegal immigrants may be increasing. Researchers peg the number of illegal immigrants in the United States at something slightly in excess of 4 percent of the total population.

"But because they are relatively young and have high birthrates, their children make up a much larger share of the newborn population and the child population in this country," the report says.

The report does not say how many of those 5.1 million children of illegal immigrants are in Arizona.

But Passel pointed to an earlier study that concluded Arizona is home to about 4.2 percent of all the illegal immigrants in the U.S.

Using that as a rough estimate, it translates to more than 214,000 Arizona children from birth through age 17 who have at least one illegal-immigrant parent, and based on the Pew figures nationwide, an estimated 170,000 were born in this country.

The numbers will figure in the debate over the future of the 14th Amendment to the Constitution.

The amendment, adopted on July 9, 1868, says anyone born or naturalized in the United States is a citizen of both the U.S. and the state where the person lives. Courts have interpreted that to mean citizenship is granted to those born in the U.S. regardless of whether one or both parents had no legal right to be here.

Some people, including Arizona Sen. Russell Pearce, R-Mesa, argue that those court rulings are flawed. Pearce noted that the amendment makes it conditional on the children being "subject to the jurisdiction" of this country. Pearce said courts, citing that language, had concluded for years that it did not entitle American Indians to citizenship.

"There's no doubt where they were born," he said. It was only after Congress specifically altered the law regarding citizenship for Indians that the situation changed.

Pearce is weighing whether to push for Arizona to bring a new challenge to those court rulings.

That would take the form of a state law denying birth certificates to children born in Arizona unless it could be shown that at least one parent was in the U.S. legally. That likely would provoke a lawsuit.

But Pearce said a simpler course would be to have the issue handled at the federal level.

U.S. Sen. Lindsey Graham, R-S.C., is pushing to amend the Constitution to spell out that mere birth within U.S. borders does not entitle someone to citizenship. But that process is long and involved, and difficult to achieve.

On StarNet: Go to this article at border to respond to a StarNet poll about children born to illegal immigrants and to see a PDF file on this subject from the Pew Research Center.

Applicable language of the 14th Amendment

All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.

Star reporter Brady McCombs contributed to this story.