The action "calls into question the very integrity of Department of Justice policies toward the press and its ability to balance, on its own, its police powers against the First Amendment rights of the news media and the public's interest," said a letter released yesterday by the coalition.
The protests came after the US government claimed it was trying to protect American lives when it took the drastic step of seizing journalists' phone records in a probe of what it calls a major security breach.
Attorney General Eric Holder yesterday defended the action, saying it was part of a probe into a security breach which had put the American people at risk.
"I've been a prosecutor since 1976. And I have to say that this is among, if not the most serious ... A ... Very, very serious leak," Holder said.
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The investigators' action is believed to be linked to a probe into a story on a foiled terror plot, which they suspect contained leaked information.
The AP said its story disclosed details of a CIA operation in Yemen that stopped an Al-Qaeda plot in 2012 to detonate a bomb on an airplane bound for the United States.
Holder said he had rescued himself from the probe because he was interviewed by the FBI about unauthorized disclosures in the matter.