MILAN, Sept 15 (Reuters) - Hong Kong-listed Italian luxury group Prada SpA said on Thursday it had bought a stake in the Tuscan tannery Superior SpA, tightening its grip on its supply chain, but noted it had not decided whether to list in Milan.

A dual listing in Europe would help Prada widen its investor base, as some investment funds can only put money in European or U.S. stocks.

"No decision has been taken," on a secondary listing in Milan, Chief Executive Patrizio Bertelli said in an interview with Italian daily newspaper Il Corriere della Sera.

In July, Prada's Chairman Paolo Zannoni said a secondary listing in Milan was a possibility but not a priority for Prada.

Last month Bloomberg News reported that Prada was considering seeking at least $1 billion from a secondary listing in Milan and was working with Goldman Sachs on early preparations.

Italian daily newspaper Il Sole 24 Ore reported on Tuesday that Prada aimed to list in the Milan stock exchange next year.

Tuscany has been booming as high-end fashion houses scramble to meet a strong wave of global, post-pandemic demand for luxury accessories, expanding their factories and buying artisan workshops.

Based in Santa Croce sull'Arno, near Pisa, Superior is a leader in calfskin processing and has been active for more than 60 years in the Italian and international markets as a specialised tanner for the luxury sector, Prada said.

Under the agreement, Prada bought a 43.65% stake in Superior, whose management responsibility will remain with the current CEO, Stefano Caponi.

"The acquisition of a shareholding in Superior represents another important step in the strategic direction towards vertical integration of the Prada Group's supply chain," Bertelli said. (Reporting by Gianluca Semeraro in Milan and Mimosa Spencer in Paris; editing by Maria Pia Quaglia and Keith Weir)