PHOENIX -- Federal prosecutions of immigration cases surged 16 percent in fiscal year 2009, according to Department of Justice data analyzed by a Syracuse University research center.

Prosecutors filed 91,899 immigration cases between October 2008 and September 2009, according to researchers.

Most cases involve illegal immigrants who agreed to return to Mexico to avoid jail time.

Maricopa County Sheriff Joe Arpaio said the federal government is going too easy on people who cross the border illegally.

“You want to be tough on illegal immigration,” he said. “You prosecute people that do that and put them in jail.”

“You tell everybody, ‘You cross that border, you’re going to jail. Period,'” said Arpaio.

He said the federal government should also work more closely with the Mexican government to help develop its economy so Mexican citizens have more opportunities for work.

Arpaio also said the federal government should also put more pressure on the Mexican government help U.S. efforts to reduce illegal immigration.

Valley immigration lawyers agree that the rise in federal prosecutions is an ineffective way to tackle the illegal immigration problem.

“These types of prosecutions that are flooding our federal immigration courts involved extremely low level, not major, criminals,” said Gerald Burns, who heads the Arizona chapter of the American Immigration Lawyers Association, “Not rapists, not murderers, not drug pushers and peddlers.”

Burns is also concerned the quick plea deals reached by prosecutors could be violating illegal immigrants’ rights.

"Federal immigration laws does provide for due process and there's a real concern that people are being kind railroaded out of the country,” he said.