Police said the woman had come to Milan for a photo shoot, apparently a fake setup, and was abducted on 11 July. The 20-year-old has given statements to police.
It has been reported that the captor demanded £50,000 upon the woman's release and threatened to kill her if she told police about the incident.
They continued that the 20-year-old was kept chained to a wooden dresser in the farmhouse while her captors attempted to sell her on the dark web for more than £230,000 and demanded the model's agent pay to secure her safe release.
He said he was working for The Black Death Group.
The police say the man, Lukasz Pawel Herba, 30, a Polish citizen who lives in the United Kingdom, was charged with kidnapping for extortion purposes.
Prosecutors described the kidnapping as a "very well-organised seizure" and added he was contacted over the internet two days later with requests to "buy" her for sexual purposes.
Her kidnapper reportedly demanded €300,000 off her agent in the United Kingdom to prevent her "sale" online.
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Police said she was held for a week in abandoned offices in the city and officers are now looking for accomplices.
The man has confessed to the crime and his phone and computer - including photos of the model being offered on the "deep web" - have been confiscated.
Investigators are exploring the possibility the woman was abducted so she could be auctioned off online as a sex slave, according to reports.
Police found a small bedroom at the property, but it is unclear whether it was used by the model or the kidnapper.
On July 17, for reasons that are not clear, Herba drove the woman back to Milan and released her close to the British Consulate, where he was arrested.
The woman was released after being held for six days and investigations are being carried out by authorities in Italy, Poland and the UK.