Disturbing, raw and graphic – so was Francis Bacon inspired by the Nazis?

Francis Bacon appropriated Nazi propaganda for some of his most important paintings to explore "man's capacity for savage violence", a leading art historian claims.

Critics have long ignored the depth of inspiration the painter drew from fascist imagery despite "compelling" visual evidence, Martin Hammer says. Several of Bacon's most violent works, which are generally interpreted as sexual and autobiographical, actually contain "submerged" attempts to deal with the horrors of Hitler's regime, he argues in his book, Francis Bacon and Nazi Propaganda.

It aims to shed new light on one of the greatest British artists of the 20th century. Hammer, professor of history and philosophy of art at the University of Kent, said: "The use of Nazi imagery in Bacon's work was an important aspect of his creativity; it is present in many works. It was something that hadn't been addressed."

Where contemporaries sought to bury wartime memories, Bacon appropriated and transformed Nazi photography, using the imagery as a springboard for works painted over 20 years. The professor says it is remarkable that Bacon's Nazi aesthetics have not been scrutinised before: "The visual evidence is compelling, but it's hard to know what to make of it. It's open to interpretation."

Bacon was born in 1909. He experienced the Blitz in London, but unlike many of his contemporaries he did not participate in the Second World War or become a war artist. Professor Hammer said: "Bacon started working with this imagery, looking at the true nature of the regime that had emerged. He used it to explore the instinctive, savage, bestial nature that was dominating everyone's lives."

The influences came from photographs and posters, often by Heinrich Hoffmann, a photographer close to Hitler. Many of the German images were recycled in books and magazines in the UK, Professor Hammer said.

"There was a horrified fascination with the image of Hitler and the Nazi leadership." The book refers to a painting of a "screaming orator-like figure with a military helmet, it clearly sets up the Nazi leadership as these grotesque creatures. You get a sense of his horrified reaction to this culture."

The professor added: "His earliest pictures using Nazi imagery were pretty obvious, which is why he abandoned them. Increasingly these references were submerged."

In his book, published next month by the Tate, Professor Hammer addresses the question of how and why Bacon appropriated the Fascist imagery. The trigger for the book, was the major Bacon exhibition at the Tate Britain in 2008.

"It started a purely visual observation. I noted the parallels between one or two of the paintings and certain Nazi images I was aware of," he said. That started a process of research that accumulated a whole series of other images. "It got to the point where I felt this was a consistent feature of Bacon's work from the 50s and 60s."

Bacon never referred to the Nazis, "largely because he wasn't asked about it. Interviewers either didn't recognise it or thought it shouldn't be talked about," Professor Hammer said.