White House reporters and photographers on Thursday accused top officials of deliberately blocking access to President Barack Obama and of substituting its own "visual press releases" for independent news coverage.

In a letter to White House spokesman Jay Carney, the White House Correspondents Association (WHCA) and other news organizations said the practice belied the administration's frequent claims to a new level of transparency.

The letter registered alarm that the White House bans coverage of Obama at certain events, deeming them private, but later releases photographs and videos from its own in-house news and public relations operation.

"Journalists are routinely being denied the right to photograph or videotape the President while he is performing his official duties," the letter said.

"As surely as if they were placing a hand over a journalist's camera lens, officials in this administration are blocking the public from having an independent view of important functions of the Executive Branch of government."

"You are, in effect, replacing independent photojournalism with visual press releases," the letter told Carney, calling the practice a "troubling break from tradition."

White House photographers have long been frustrated at the activities of White House official photographer Pete Souza who has distributed hundreds of candid shots of Obama and other officials in meetings and settings from which the press is barred.

The shots go out on a Flickr feed, Instagram and Twitter, where Souza has 94,000 followers.

The letter listed a half dozen recent instances where news coverage has been banned of events the WHCA considers of great public interest, for which photographers were barred and official photos were released.

They include a meeting between Obama and the co-chairs of the US-China Strategic and Economic dialogue in July and talks the same month between the president and Vice President Joe Biden and Middle East peace negotiators.

The list also included a meeting between the president and First Lady Michelle Obama and Pakistani human rights activist Malala Yousafzai in the Oval Office in October.

While official White House photographers have existed for years, and have access to private meetings from which journalists and photographers have long been barred, the WHCA contends in the letter, which AFP signed, that this administration has crossed a line.

Privately, White House journalists complain that official administration pictures unfailingly portray Obama in a flattering light, and lack the authenticity of independent news coverage.

At a time of austerity in the news business, with traditional clients cutting subscriptions due to online competition, some photographers view the White House operation as tantamount to a rival photo wire service which threatens their livelihood.

There was no immediate comment from the White House.