WASHINGTON – Federal prosecutors have pursued hundreds of thousands more cases against immigrants in the country illegally under President Obama than they did under the previous two White House administrations combined.

Almost 680,000 federal immigration charges have been filed in the last eight years, up from about 287,000 under President George W. Bush and fewer than 100,000 under President Bill Clinton, according to figures compiled by a university research center that tracks federal law enforcement.

David Burnham, co-founder of the Transactional Records Access Clearinghouse at the University of Syracuse, said the increase represents a joint crackdown by lawmakers and the Justice Department under Obama.

"This outcome is a combination of policies and actions by a very aggressive Congress and a very aggressive Obama administration both wanting to work the borders — keep people out, as Mr. Trump says," Burnham told McClatchy.

Obama has long been described as the "deporter in chief" by immigration advocates who dispute President-elect Donald Trump's characterization of Obama as soft on immigration.

But the new numbers provide the first concrete evidence of how Obama's record compares with his predecessors'.

Burnham's group, which aggregates raw data it obtains from the Justice Department, provides monthly updates of the figures on its website and sends out news releases each year when it compiles annual numbers. It just released figures for the 2016 federal fiscal year, which ended Sept. 30.

While U.S. attorneys in the 50 states and the District of Columbia decide whether to file federal immigration charges, Burnham said such a big gap in filings between the current and previous administrations wouldn't be possible without a stern policy set at the top.

"The charges that President Obama is not doing anything on immigration just don't fit the facts," he said.

Partly as a result of the increased number of federal prosecutions, deportations have also been at record highs since Obama took office in January 2009.

In the first seven years of Obama's time in office, from 2009 through 2015, his administration deported 2.5 million people, according to the Department of Homeland Security.

Many of the deportees had been convicted on immigration charges or for unrelated different crimes. An additional 2 million people were given the choice of departing the country "voluntarily" or face criminal proceedings and chose to leave, but the government does not classify those exits as deportations.

More than 80 percent of those deported last year were for what the administration terms "priority one" crimes, which range from various felonies to joining violent gangs or getting caught at the border while trying to enter the country illegally.

During Bush's eight years in office, 2 million people were deported.

Obama and Bush together deported more people than all previous presidents combined.

Trump has vowed to deport 2 million criminal aliens, a figure that's lower than Obama's record. But one group Trump could go after that Obama has shied away from is immigrant families and people with a long record of having lived and worked in the United States.

"Felons, not families," Obama said two years ago. "Criminals, not children. Gang members, not a mom who's working hard to provide for her kids."

To help enforce such distinctions and with immigration reforms mired in Congress, Obama took two executive actions on his own.

In June 2012, Obama issued a policy called Deferred Action for Childhood Arrivals, or DACA. It directed enforcement agencies not to deport people who'd entered the country before the age of 16 and before June 2007.

More than two years later, the president followed up with Deferred Action for Parents of Americans.

That policy, known as DAPA, shielded people who had lived in the United States since Jan. 1, 2008, had arrived before June 2007 and have children who are U.S. citizens or hold green cards.

Trump has pledged to "immediately terminate" both policies. He criticized DACA as "one of the most unconstitutional actions ever undertaken by a president."

That policy has been in limbo since June, when the Supreme Court in a 4-4 decision let stand a lower court's ruling that Obama had exceeded his executive authority by implementing it.