Washington (CNN) The United States has dropped 29 spots in the annual Reporters Without Borders press freedom ranking since 2009, when President Barack Obama took office.

The U.S. ranked 49th this year out of 180 countries included in the organization's World Press Freedom Index , joining the ranks of countries like Niger, Malta and Romania.

The decline from its position at No. 20 in 2009 has been spurred by the Obama administration's aggressive prosecution of whistleblowers, said Delphine Halgand, the organization's U.S. director.

"We consider that the Obama administration has launched a war against whistleblowers," Halgand said. "This year is a continuation of the concern we already expressed that national security protection has been more and more threatening freedom of information in the U.S."

The U.S. has prosecuted eight alleged whistleblowers under the Espionage Act, more than all previous presidential administrations combined, Halgand said.

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