Dozens of leading U.S. press organizations are urging the Obama administration to live up to its transparency promises and reverse a trend of increased secrecy at federal agencies.

Thirty-eight national press organizations and transparency groups—including the Society for Professional Journalists, Investigative Reporters and Editors, and the Poynter Institute—called on the Obama administration to end "politically driven suppression of news and information about federal agencies," in a letter to the White House released Tuesday.

"Over the past two decades, public agencies have increasingly prohibited staff from communicating with journalists unless they go through public affairs offices or through political appointees," the letter reads. "This trend has been especially pronounced in the federal government. We consider these restrictions a form of censorship—an attempt to control what the public is allowed to see and hear."

Specifically, the letter points to numerous instances of federal public affairs officers blocking reporters’ requests to talk to agency staff, delaying responses to interview requests, and blackballing reporters who write critically of agencies.

According to the letter, "a recent survey found 40 percent of public affairs officers admitted they blocked certain reporters because they did not like what they wrote."

The organizations are asking the Obama administration to issue a memo not only telling employees at federal agencies they are free to speak with reporters, but also encouraging them to. The letter also requests the administration create a way to report incidences of suppression or stonewalling of media requests.

"The practices have become more and more pervasive throughout America, preventing information from getting to the public in an accurate and timely matter," said David Cuillier, president of the Society of Professional Journalists in a statement. "The president pledged to be the most transparent in history. He can start by ending these practices now."

Shortly after assuming office in 2009, President Obama pledged to run "the most transparent administration in history," and the White House has stuck to the line, despite numerous complaints and studies that indicate the Obama administration is little better, and in some cases worse, than its predecessor.

Last year, the Committee to Protect Journalists released a scathing report on the Obama administration’s attempts to control media access.

"The Obama administration’s aggressive war on leaks, and its determined efforts to control information that the news media needs to hold the government accountable for its actions, are without equal since the Nixon administration and in direct conflict with President Obama’s often-stated goal of making his administration the most transparent in American history," former Washington Post executive editor and report author Leonard Downie, Jr. said.

The New York Times’ David Sanger told Downie the Obama administration is the "most closed, control-freak administration" he has ever covered.

The White House did not immediately respond to a request for comment.