On 6 February, collectors with very deep pockets will have a rare opportunity to bid for a major work by Italian figurative artist Amedeo Modigliani. Christie’s auction house in London is making confident noises about the 1919 portrait of the Italian painter’s lover Jeanne Hebuterne selling for as much as £22m.

Modigliani owners are no doubt keeping their fingers crossed for a lucrative sale, for this would suggest the market is bouncing back from a recent, less salubrious, episode which had threatened to knock it for six.

Before Christmas, shocked modern art experts in Italy spoke of an “earthquake” tearing through their genteel world following the arrest of Modigliani expert Christian Gregori Parisot. If you wanted to check the authenticity of an work said to be by the Italian artist, Parisot was, or had been, your man.

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Who better than the art trader who had lived and breathed Modigliani for decades, who met and worked with the painter and sculptor’s daughter Jeanne in the early 1980s? Or at least that was what he’d have you believe. In reality the case of Mr Parisot has revealed a remarkable degree of gullibility in the art world – and has called into question the ease with which people are able to assume the role of trusted authority.

Parisot, with his impressive-sounding title of President of the Archives Legales Amedeo Modigliani, organised Modigliani exhibitions around the world. And his say-so was enough to decide whether a sketch, painting or sculpture was the real thing. He had even worked as a consultant for the Italian state’s Cultural Heritage Protection agency, charged with the protecting the country’s important artistic heritage from con men and charlatans. Officials were forced to admit as much last month when he was arrested for forging and fraudulently endorsing dozens of fake Modiglianis.

Along with Parisot and his suspected accomplice, the art dealer Matteo Vignapiano, the police seized 59 fakes including 41 sketches, 13 graphic designs, four sculptures in bronze and an oil painting.

As is so often the case with such extraordinary scams, the clues were there but people only started to notice them after the event. Claudio Strinati, a senior official at the Ministry of Cultureand president of the “scientific committee” of Parisot’s “Modigliani Institute”, has admitted that it had seemed odd that the committee never actually met.

“Parisot asked me to do this job, years ago,” he said, “But the committee never met, at least to my knowledge, and has never done, [let alone] decided or verified anything. I thought it was strange, but not to the point of imagining illegal activities.”

Modigliani’s pared-down, masque-like faces may have been relatively easy to fake. But given this, it is not unreasonable to expect experts such as Mr Strinati ,who were charged with verifiying his works, to have been more a little more active.

The irony of the situation won’t be lost on students of Modigliani’s tragic life. For while fraudsters have been getting rich on fake Modiglianis. During the artist’s pestilential existence – he died aged 35 when tuberculosis spread to his brain – the destitute alcoholic and drug addict was forced to give away his paintings in exchange for food and only ever managed one solo exhibition in Paris. And that was closed down on the first day following complaints of indecency.

Italian detectives brought the curtain down on Parisot after raiding a show titled “Modigliani from Classicism to Cubism” at the Archeological Museum in Palestrina, near Rome, in July 2010. It was here that true authorities identified 22 fake Modiglianis.

The most remarkable fact, however, relates to the conviction Parisot acquired in Paris two years before this major exhibition in a state gallery.

In May 2008, The Art Newspaper reported how “the art historian and Modigliani specialist Christian Parisot was sentenced to two years in prison with 16 months suspended, and fined €8,000 by a Paris court on 18 April, for faking drawings by Jeanne Hébuterne, Modigliani’s mistress and model”.

The works were seized by the police after Luc Prunet, Jeanne’s great nephew, complained they were forgeries. This was confirmed in a report by the French expert Gilles Perrault. But even this wasn’t enough for the art world to sit up and take notice.

No-one is currently answering the phone at the Archives Legales Amedeo Modigliani, in Rome. But other experts are clear about they see as the problem to be. “Any group, entity or individual can set themselves up as “authorities” with pretentious names,” lamented Martin Kemp, a professor of art history at Oxford University and a leading authority on Leonardo da Vinci.

It remains to be seen if the 100 or more bogus Modiglianis that Parisot is thought to have put on the market have dented demand for the artist. There is no doubt that the 1919 portrait of the Italian painter’s lover Jeanne Hebuterne on sale at Christie's is genuine. And Christie’s hopes that if anything, the clamour for genuine works by the Italian artist will have increased. Hence its upbeat predictions for the imminent auction of the key portrait.

Jay Vincze, Christie’s impressionist and modern art specialist, noted that Modigliani produced relatively few paintings during his short life. Perhaps gallery owners and art traders ought to have considered this before they listened to Mr Parisot – and allowed greed to get the better of them.

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The picture shown above is Amadeo Modigliani’s Portrait of Jeanne Hebuterne, an internationally celebrated masterpiece and an unquestionably genuine work by the artist which will be offered at auction on 6 February 2013 at Christie’s, London. We are happy to reiterate the position for complete clarity.