The diary of Friedrich Kellner, a lowly bureaucrat in wartime Germany, claims the average citizen was aware of the Nazis' atrocities

The German people knew of the Nazis' appalling crimes throughout World War Two, an explosive new book claims.

The secret wartime diary of Friedrich Kellner, a lowly bureaucrat, reveals he was in active opposition to Hitler.

On December 17, 1942, he wrote in the 200,000-word diary: 'Adolf Hitler… is Satan and the devil in one person.'

And he reveals just how much the average German citizen knew about Hitler's crimes - even towards the beginning of the Second World War, reports the Daily Express.

In October 1941 Kellner wrote about German soldiers returning from the frontline and noted the 'inhuman atrocities' on the eastern front 'as naked Jewish men and women were placed in front of a long deep ditch and upon the order of the SS were shot by Ukrainians in the back of their heads.

'Then the ditch was filled in as screams kept coming from it'.

In October 1941 Kellner wrote about German soldiers returning from the frontline and noted the 'inhuman atrocities' on the eastern front. It raises questions about who knew what

Kellner's grandson, former American serviceman Robert, said: 'If he knew, it is clear that the average German did know what the Nazis were doing. The existence of the diary means it can never again be claimed that the Nazis were acting in secret.'

Robert was first shown the diary, now a book titled My Opposition, in 1960 when he travelled to Germany to meet his grandfather.

He was expecting to meet a Nazi, like his father, but instead found a man deeply against the evil group.

Shortly after Robert arrived, Friedrich crouched down in front of a cabinet in his drawing room and brought out the secret manuscript.

Friedrich was born in 1885 and worked as a courthouse administrator in the small German town of Laubach, central Germany, where he had moved in 1933 to escape persecution for his socialist views.

He knew he had to exercise 'extreme caution' in criticising the Nazis and confined his criticism to the diary.

Kellner's grandson, former American serviceman Robert, said: 'If he knew, it is clear that the average German did know what the Nazis were doing

The diary has just been released in Britain following its publication in Germany last year.

But it was only released when former President George Bush Senior intervened to have it put on display in 2005 after spotting its significance.

But publishers still had to overcome Germany's strict libel laws and the country's decision not to 'point fingers'.

But Robert was determined to publish the diary to dispel the myth that the German people were unaware of the Nazis' atrocities.

He said Friedrich wrote the book so future generations would know the truth.