Weak sales in Asia Pacific outside of Japan and in the United States failed to offset an improved picture in Europe, where the weak euro bolstered sales to bargain-hunting tourists from outside the region.
Total revenue at a group which includes clothes line Miu Miu and upmarket cobbler Church's totalled 3.545 billion euros, broadly in line with expectations but slightly below a figure of 3.552 billion euros registered in 2014.
Sales in Asia Pacific outside Japan were down 4.0 percent at current exchange rates and 16 percent at constant rates.
A stronger dollar hit sales in the United States by making purchases of pricey handbags and other luxury products significantly more expensive for visitors planning to splash the cash on vacations.
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The opposite trend was witnessed in Europe where the weaker euro ensured sales at constant exchange rates were up five percent on what the company described as "a steady stream of tourists, especially from Asia Pacific and the US."
Japan registered sales growth of 11 percent (4.0 percent at constant exchange rates).
"These two factors have made prices fluctuate widely and diverted tourist traffic in sudden and unpredictable ways," Bertelli said.
Some fashion commentators have suggested that Prada's problems go beyond economic issues with the brand having arguably become dangerously associated with conspicuous consumption during China's boom years. As a result it is now seen as being snubbed by young trend-setters.
"Our retail network - now truly global thanks to investment in recent years - enables us to keep developing a direct relationship with our ever more demanding customer all over the world," he said.
He said Prada was planning new commercial and marketing initiatives and "an extensive digital project" to strengthen dialogue with customers.
"These actions, taken against the background of rigorous and disciplined cost control, will enable us to consolidate our market position with satisfactory margins and returns on investment," said Bertelli, the co-founder of the group along with his wife, creative director Miuccia Prada.