Oh, my god! Look familiar?

The Berlinische Galerie is a spectacular museum in Berlin, with an outstanding collection of pre-Hitler modernist art – most of the kind of work he called "degenerate". We were being shown around by Rudolf Brunger, one of the founders of the landmark cultural and ecology centre ufaFabrik when my wife Pamela shouted out, "Oh, my god!" I turned around and said the same thing.

In front of us was a model that looked like nothing if not the Sydney Opera House. It was marked: "Sternkirche [Star Church] 1922 by Otto Bartning".

The Sternkirche ... the similarities to the Opera House are remarkable and it may have unconsciously inspired Joern Utzon.

I started searching on the web and could find no reference where Danish architect Joern Utzon mentioned this Bartning creation as an inspiration. Why had Utzon not mentioned this?

I emailed the image to some experts in Australia and overseas, asking if this was plagiarism, "unconscious borrowing", influence, improper appropriation or homage.

In court, a jury of laypersons can decide but I sought some expert eyes. I had no dog in this fight but it was intuitively weird to me that Utzon had never mentioned Bartning's Sternkirche. The master said his inspiration was the work of Sweden's Erik Gunnar Asplund, Finland's Alvar Aalto, American Frank Lloyd Wright, a 12th-century Chinese guide to building regulations and sliced oranges.

Utzon later said words to the effect that the Opera House was a (modernist) Gothic cathedral. Exactly what the Sternkirche model was.

From London, Lutz Becker, historian, curator and specialist in Weimar art and architecture, confirmed that Sternkirche 1922 was famous then and now in Europe.

"The Bartning church is of course a great aesthetic inspiration, a famous piece of European design history, undoubtedly known to an architect with international ambitions," Becker said.

"Bartning was indeed a very important architect but is now mostly forgotten. The Sternkirche project of 1922 is well known, particularly to people who are interested in expressionism and its bold but unbuilt plans.

"The Bartning church was ahead of its time – it could have only been built in freely suspended concrete skins, of which the technique was not available till the 1950s.

"Aalto and Bartning knew each other and the Finn was next to the Italian, [Pier Luigi] Nervi, as one of the few architects who could handle such structures.

"Utzon is influenced by all that and was able to build his structure based on a rich experience and historical knowledge of concrete construction.

Star Church does have obvious similarities to the Opera House and I would have no doubt that Utzon would have been aware of it.

"The Bartning idea may well have influenced the design of the Opera House. Not plagiarism as such but, as you describe it, an undisclosed source or 'unconscious borrowing'."

Ursula Muller, head of the architectural collection at the Berlinische Galerie, confirmed she saw the similarities but dismissed any notion that Utzon "stole" his idea from Bartning.

"That is ridiculous, following this argument one could accuse all cubism painters to have stolen their ideas from Picasso," she said.

However, this is not the argument since all painters acknowledged Picasso and Braque as the source.

Veteran Australian modernist architect, Peter Burns, 86, entered the same design-the-opera-house competition that Utzon won in 1957.

Burns had never heard of Bartning. "We were not well travelled in those days," he said. "But I see the very interesting visual links between the two works, the dates work and if I had seen that Sternkirche, it is an image that would have stuck with me."

Australian architect Chris de Campo said: "I see the links ... on the surface of it I do share any quick assumption or perception that the Star Church does have obvious similarities to the Opera House, and I would have no doubt that Utzon would have been aware of it, as any studied architect abreast of the movements of their time would have, and particularly with Utzon's closer links: Aalto, modernism, the avant garde and structural investigation."

De Campo listed similarities between the Opera House and the Star Church, adding: "Thus I feel that the similarities are there and the questions should undoubtedly be asked as to the influence or, more so, the inspiration that could have been born from Utzon's knowledge of Bartning's church or simply an acknowledgement."

But he believes Utzon's Opera House went much further and that he was a genius, instilling poetry and unique structure.

"I wouldn't go anywhere near plagiarism or the like as the Opera House, in realisation, abounds in complete and comprehensive masterstrokes by the great man. Anyway, as noted at the start, the links are more than visually obvious, and it is worth asking the questions and making the connections, more so for a richer understanding of the creator and his Opera House."

A colleague in Sydney asked Utzon's son, Jan, if the family was aware of any such links. The response was unenlightening. "I have no idea. My father may have seen this project but I'm sure that it has had no influence on his concept for the Opera House. The design for the Opera House was the result, or the design-response for a solution to cover the 'buildings/venue' underneath." He is saying, in a non sequitur, that the outside design was for covering the inside.

Someone else pointed me to a comment by artist Frank Stella, a maker of iconic images himself, in an online remark from Architectural Record confirming the visual link that had struck us with impact.

Stella, an American artist, said: "The whole emphasis in 20th-century architecture, in all honesty, has been the flat roof. And that certainly accounts for the incredible popularity of the Sydney Opera House, which is a kind of Modern Gothic version really of ... Sternkirche. It's kind of amazing that [expressionist architecture] has been hidden for so long actually."

My research revealed some darker elements to this unfolding mystery. It emerged that Aalto, who was Utzon's key Finnish mentor and architect, was a straight-out Nazi collaborator. If all the experts agree on one thing, it was that Aalto – hailed as the father of Nordic modernism – was a major, if not critical influence on Utzon.

What some may not realise is that in 1943 Aalto was flown to a "rollicking" junket in the Third Reich by Albert Speer (Hitler's chief architect and armaments overseer). In a goodbye speech to his Nazi hosts at Wannsee (where a year before the Nazis had planned their "Final Solution"), Aalto said: "I do not know very much about what has been built here in the Third Reich, as because of my work in Boston I have been here so rarely. But once when I was waiting for Lawrence [sic] Rockefeller at the Harvard Club, my eyes happened to fall on a book with red covers on the shelf. I took it down and discovered that an author completely unknown to me wrote it by the name of Adolf Hitler. I opened up the book at random, and my eyes fell on a sentence that immediately pleased me. It said that architecture is the king of the arts and music the queen. That was enough for me; I felt that I did not need to read further ..."

This brought the (Nazi) house down. In 1998 this incident was raised in the United States and caused academic anger and controversy. A supporter pointed out that Aalto successfully asked Speer to rescue a Jewish colleague.

"Modernism and fascism" is a hotly contested, investigated and fascinating subject today. Many surprising minds were seduced for a while by Nazi "modernism", including psychiatrist C.J.Jung and architects Walter Gropius and Ludwig Mies Van Der Rohe.

Architecture for the masses was a Nazi theme. Speer made references to making buildings that would be good-looking ruins. Speer thus invented a theory of "Ruin Value". Utzon later parroted this in a postcard to his assistant, Bill Wheatland: "Went to Yucatan. The ruins are wonderful so why worry. Sydney Opera House becomes a ruin one day." It is reasonable to speculate that Utzon champion and Opera house competition judge Eero Saarinen, a World War II veteran of the US Office of Strategic Services (which later became the CIA), no doubt fully aware of the Nazi aspects, briefed Utzon on what was politically correct at the time to disclose or not.

The influence of fascist ideas on modern culture is a subject yet to be resolved. So it is not surprising that Utzon never mentioned any of this complex history back in 1957 or later.

Bartning, a founder of the key architectural movement, Bauhaus, with Walter Gropius, was sponsored by the Nazis and entered important Nazi architectural competitions for public buildings. A specialist in modernist churches, he avoided stigma after the war.

Fascist ghosts aside, plagiarism, and accusations thereof, are seen as a quaint, out-of-date concepts in today's postmodern culture.

The 1995 Random House dictionary defined it as the "use or close imitation of the language and thoughts of another author and the representation of them as one's own original work ... plagiarism is concerned with the unearned increment to the plagiarising author's reputation that is achieved through false claims of authorship".

Nowadays, piracy of all kinds is rampant. Some endorse this. French philosophers like Roland Barthes even theorised the very idea of an author is dead, hence copyright is irrelevant. To paraphrase, you cannot plagiarise because originality does not exist – everything is from something else.

A quick survey revealed recent litigation on architectural plagiarism. A big case, Shine v Childs, was settled in 2006 involving the Freedom Tower design in Manhattan, which was to replace the World Trade Centre's towers. The New York Times cracked: "A suit over the Freedom Tower revives an old question: Is imitation the sincerest form of architecture?"

Architect magazine reported: "Courts typically analyse substantial similarity under what is commonly known as the "total concept and feel" test. In practical terms, this means that an infringing work is substantially similar to a copyrighted work if an ordinary observer is disposed to overlook the differences between the works and regard their aesthetic appeal as the same".

By this recent standard the late Bartning had a case against the late Utzon.

This recalls the Tom Lehrer song:

Plagiarise,

Let no one else's work evade your eyes,

Remember why the good Lord made your eyes,

So don't shade your eyes,

But plagiarise, plagiarise, plagiarise –

Only be sure always to call it please 'research'."

But to my mind it's a matter of degree and if a work is distinctly similar to another, it should be acknowledged. In this case, we refer to one of the most famous buildings in the world, so origin is of interest .

Certainly to the naked eye the Opera House looks like an uncredited, close appropriation of Bartning's plans, model and concepts, particularly if one blocks out either half of the Bartning model.

One can argue that there is a fine line between plagiarism, influence, "unconsciousness borrowing" and so on. But that Utzon was never known to have mentioned Bartning is troubling. There is little doubt he would have been at least aware of his work.

In the fine arts, the creative chain of title, and who thought of what first, is paramount in determining an artist's or architect's importance.

As my brother, Tiriel Mora, said in the film, The Castle: "It's the vibe, your honour!"

What do you think? Email your comments to [e-mail].