An Alfred Hitchcock documentary about the Holocaust, which was suppressed for political reasons, is to be screened for the first time in the form its director intended after being restored by the Imperial War Museum, reports the Independent.

Hitchcock was asked to assemble footage shot by a British army film unit cameraman of the liberation of the Bergen-Belsen concentration camp in 1945. But the resulting documentary, which had been commissioned in an attempt to inform and educate the German populace about the atrocities carried out by the Nazis in their name, was ultimately held back.

It was not shown at all until 1984, in an incomplete version at the Berlin film festival, and was missing a sixth reel and in poor quality when it was screened on the PBS network in the US a year later. Now the film, retrospectively titled Memory of the Camps, is to finally see the light of day in a format Hitchcock would have approved of.

"It was suppressed because of the changing political situation, particularly for the British," Dr Toby Haggith, senior curator at the Imperial War Museum, told the Independent. "Once they discovered the camps, the Americans and British were keen to release a film very quickly that would show the camps and get the German people to accept their responsibility for the atrocities that were there."

Haggith said the film, shown at test screenings, extremely disturbed colleagues, experts and film historians. The film's narration, which has been re-recorded with a new actor, features descriptions of "sightseers" at a "chamber of horrors".

"The digital restoration has made this material seem very fresh," said Haggith. "One of the common remarks was that it [the film] was both terrible and brilliant at the same time."

The film is due to be broadcast on British television in 2015 to mark the 70th anniversary of the liberation of Europe. It will be accompanied by a new documentary from André Singer, a producer on the acclaimed 2013 film The Act of Killing, which has topped a number of critical best of the year lists, including the Guardian's. Both films will be shown at film festivals and cinemas later this year.

• Read the Guardian's top 10 documentaries

• Read Catherine Shoard's five-star review of The Act of Killing