Washington (AFP) - News agency The Associated Press on Monday demanded the FBI explain its actions in an investigation in which an agent posed as an AP reporter, calling the deception "identity theft."

In a letter to FBI chief James Comey and Attorney General Eric Holder, AP president and chief executive Gary Pruitt said the deception "corrodes the most fundamental tenet of a free press -- our independence from government control and corollary responsibility to hold government accountable."

The protest comes days after Comey acknowledged in a letter to the New York Times that an FBI undercover officer "portrayed himself as an employee of The Associated Press" as part of the effort to nab a suspect in a bomb threat case.

Pruitt argued that "this misappropriation constitutes a theft of our reputation and credibility."

"In stealing our identity, the FBI tarnishes that reputation, belittles the value of the free press rights enshrined in our constitution and endangers AP journalists and other newsgatherers around the world," Pruitt added.

Last month, documents from a 2007 court case showed the FBI created a fake Associated Press news article that appeared to have been published in the Seattle Times online, to trick the suspect into clicking a link that installed malware that would reveal his location.

Comey's revelation last week added to controversy because he acknowledged that in addition to creating the fake news story, the FBI impersonated a journalist.

Pruitt said the impersonation "erodes our ability to gather news by intimidating sources who might otherwise speak freely with our journalists and by degrading our legacy of objectivity, truth, accuracy and integrity."

He added that for AP reporters in conflict zones and those working for other news organizations "the FBI's actions put them at risk by making suspect our claim to operate separately and freely from the US government."

Pruitt said Comey's comment that such actions would be "rare" offered "no comfort for the AP and other news organizations" and added that "we need to know who approved this action in 2007, what process was followed for its approval and how the requirements today to impersonate the media are different from seven years ago."

The FBI did not immediately respond to an AFP request for comment.