A new analysis of legal and illegal immigrant counts by the Census Bureau revealed Thursday that there is a record 42.1 million in the United States, an explosion that is being driven by Mexicans flooding across the border.

In a report provided to Secrets by the Center for Immigration Studies, the total immigrant population surged 1.7 million since 2014. The growth was led in the last year by an additional 740,000 Mexican immigrants.

The 42.1 million tabulated by Census in the second quarter represent over 13 percent of the U.S. population, the biggest percentage in 105 years.

What's more, the numbers of immigrants coming and going from the U.S. is actually higher since many return home every year, said the report. "For the immigrant population to increase by one million means that significantly more than one million new immigrants must enter the country because some immigrants already here return to their homeland each year and natural mortality totals 250,000 annually," said the Center.

Ohio Gov. John Kasich, one of 17 GOP presidential candidates, joined the immigration debate and said immigrants in U.S. illegally are "contributing significantly" to the nation. AP Photo

The stunning growth is sure to pour fuel on the already white-hot immigration debate in Congress and on the presidential campaign trail.

"Illegal immigration came up in the presidential debates, but there has been little discussion of the level of immigration; this at a time when total immigration is surging according to the latest data," said Steven Camarota, co-author of the report and the Center for Immigration's director of research.

"The rapid growth in the immigrant population was foreseeable given the cutbacks in enforcement, our expansive legal immigration system, and the improvement in the economy. But the question remains, is it in the nation's interest?" he added.

Some key findings in the new report:

• The nation's immigrant or foreign-born population, which includes legal and illegal immigrants, grew by 4.1 million from the second quarter of 2011 to the second quarter of 2015 — 1.7 million in just the last year.

• Growth in the last year was led by a rebound in the number of Mexican immigrants, which increased by 740,000 from 2014 to 2015 — accounting for 44 percent of the increase in the total immigrant population in the last year.

• The total Mexican immigrant population (legal and illegal) reached 12.1 million in the second quarter of 2015 — the highest quarterly total ever.

• The Department of Homeland Security and other researchers have estimated that eight in 10 illegal immigrants are from Mexico and Latin America, so the increase in immigrants from these countries is an indication that illegal immigration has begun growing again.

Much of the new immigration is due to the explosion of green cards and the flood of younger Latin Americans leaving troubled situations back home.

Many companies, meanwhile are taking advantage of the immigrants and replacing higher paid Americans with cheaper immigrant labor, even in skilled jobs.

Polls, meanwhile, show that the public wants action to stop the surge of illegal immigrants and new foreign workers, an issue picked up by some of the Republicans running for president such as Sen. Ted Cruz and Donald Trump.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com.