Rights groups say national security priorities have a "chilling effect" on journalists who fear jail time for reporting confidential information. Allison Shelley/Getty Images

Pervasive national security and surveillance programs have scaled back press freedom in established democracies like the United States, Reporters Without Borders (RSF) said in its World Press Freedom Index released Tuesday.

In an index that usually shifts incrementally from year to year, “for the first time, the trend is so clear,” Delphine Halgand, the group’s U.S. director, told Al Jazeera. She said the "chilling effect" on investigative journalists fearful of government prosecution is most palpable in the U.S.

“After 2013, we cannot deny any more that in the U.S., the whistle-blower is the enemy,” Halgand said. “The U.S. is going after confidential sources, compromising the only possibility to do a real journalist’s work."

The annual index assigns each of 180 countries a score based on factors ranging from pluralism of perspectives and independence of media from the authorities. In 2014, as has traditionally been the case, the Northern European nations of Finland, Netherlands and Norway topped the list while Turkmenistan, North Korea and Eritrea floundered at the bottom.

But other longstanding stalwarts of media freedom took a dive in 2013, which the group attributed to a “disturbing” trend of prioritizing national security over democratic freedoms.

“Freedom of information is too often sacrificed to an overly broad and abusive interpretation of national security needs, marking a disturbing retreat from democratic practices,” RSF said in a press release.

Investigative journalism, like that which exposed the United States’ far-reaching NSA data collection programs, has been the foremost casualty, the index said.

The U.S. dropped 13 places to 46th globally, due primarily to its pursuit of whistle-blowers like Edward Snowden, the ex-intelligence contractor who has been leaking information about the bulk collection of phone data and spying on allied foreign leaders by the NSA, as well as others involved in leaking documents.

NSA surveillance programs have weathered a firestorm of condemnation from rights groups concerned that the bulk collection violated First and Fourth Amendment rights and undermined the U.S.’s reputation abroad.

The whistle-blowers who have exposed these programs, including Snowden and U.S. Army soldier Chelsea Manning, who was convicted in July of leaking confidential documents, have been targeted by the government under the Espionage Act. The journalists who report on such confidential information are often pressured to reveal their sources, undermining what Halgand called "the lifeblood of investigative journalism."

New York Times reporter James Risen has been forced to testify against ex-CIA officer Jeffrey Sterling, also charged under the Espionage Act. Freelance journalist Barrett Brown faces 105 years in prison for his involvement in leaking information from private intelligence company Stratfor.

“Virtually all info about national security is considered confidential, which means the crackdown is designed to restrict all but the approved version of things,” Halgand added.

In total, eight whistle-blowers have been charged under the Espionage Act (of 1917) since President Barack Obama took office in 2009 — compared to just four under all previous administrations.