Peter Büttner claimed that the popular 19th-century novel by Swiss children's author Johanna Spyri was at least inspired by an earlier German tale.
His assertion was highlighted in a recent documentary broadcast on Swiss television, rankling the country's Alpine foothills where the fictional blonde, ponytailed young girl is regarded as one of their own.
It has also fuelled traditional German-speaking eastern Swiss animosity towards what they regard as the "arrogance" of their big northern neighbours in Germany.
Büttner, a specialist in German culture and literature, said he came across a largely forgotten short story while conducting research in Frankfurt. Entitled "Adelaide, the Girl from the Alpine Peaks" ("Adelaide, das Mädchen vom Alpengebirge"), the tale was written by a German author named Adam von Kamp.
"I immediately noticed the same narrative structure: a little girl brought up by her grandfather, who left her homeland and grew unhappy abroad until she could go home," he explained.
Published in the early 1880s, "Heidi" - originally in two volumes - is the story of an orphan who lives with her rural grandfather in the pristine Alpine meadows.
She becomes homesick when she is forced to join her aunt in the German city of Frankfurt, where she faces a disciplined education.
But the sequel a year later brought a happy ending as Heidi escapes urban life to return to her rural idyll and friends.
The story struck a chord in the late 19th century. While its charm crossed borders - the book has been translated into dozens of languages and millions of copies sold world-wide - its impact back home was enormous. "Heidi" swiftly became an inherent part of Swiss popular culture and lore, to the extent that the frontiers between fiction and reality are today sometimes blurred.
'I never wanted to take Heidi from the Swiss'
"The story is popular in Switzerland because so many people find it familiar," said Judith Stump, owner of the village shop in Maienfeld.
Perched 100 kilometres southeast of Zurich in the midst of rolling green hills with a snow-tipped rugged Alpine backdrop, Maienfeld was the novel's setting and is commonly dubbed "Heididorf" - Heidi's village.
The idyllic picture postcard image of Switzerland is completed by the stone and wood chalets and herds of cows out to pasture.
"I didn't say Spyri copied" von Kamp, said Büttner, denying he had accused the 19th-century Swiss author of plagiarism. "But I'm assuming that Spyri knew the work and it helped inspire her."
The German scholar also points to similarities in the vocabulary and the Swiss heroin's name, Heidi, a diminutive of the German Adelaide.
"The words used were the vocabulary of the time," retorted Andreas von Sprecher, owner of the Heidi theme village by Maienfeld.
The story also exposed a common characteristic of Swiss society a century ago, he argued.
"It was a well known feature at the time, when children from rural areas were sent to the cities," said von Sprecher, rejecting the idea that Spyri used von Kamp's work, while acknowledging that she could have read it.
Regine Schnidler, of the Swiss institute for youth and media, told the Swiss newspaper Neue Zürcher Zeitung that all the evidence indicated that Heidi's story was influenced by Spyri's experiences and her own unhappiness in Zurich.
Adelaide's story, meanwhile, runs to just 30 pages, while Heidi's is a rich fable that is 10 times as thick.
"Millions of copies of 'Heidi' have been published," underlined Büttner, currently working on a doctorate at University of Zurich.
He insists that he "never wanted to take Heidi away from the Swiss."