* Rosso takes majority stake in fashion house Marni
* OTB Holding had 1.3 bln euros revenue in 2011
* Marni expects revenues of 130 mln euros in 2012 (Adds quotes, details)
MILAN, Dec 19 (Reuters) - Diesel jeans brand founder Renzo Rosso said on Thursday he was taking control of Italian firm Marni to relaunch the bohemian-chic fashion house on foreign markets.
Marni will allow Rosso to add an upscale sophisticated brand to his youth-focused private company, Only The Brave, which also controls fashion houses Maison Martin Margiela and Victor & Rolf. Financial details of the deal to buy a majority stake were not disclosed.
Rosso said on Thursday he wanted to create a luxury conglomerate which competes on international markets but allows brands to keep their founders' identity.
"It is a shame that Italy does not have the right approach to consolidation and everybody looks inside its own courtyard," Rosso said at the presentation of the deal.
Only The Brave, whose Staff International unit also makes clothes for Just Cavalli and DSquared2, booked broadly flat revenues of around 1.3 billion euros ($1.7 billion) in 2011.
Core profit margins rose 10 percent to 14.7 percent of sales, as the group expanded into accessories and new markets.
Founded in 1994 by fur businessman Gianni Castiglioni and his Swiss-born designer wife Consuelo, Marni expects revenues of 130 million euros in 2012, mostly coming from outside Italy.
The Lugano-based company, which directly manages 100 stores of which two only are in Italy, competes with bigger powerhouse Prada for its futuristic, unconventional style.
Italy is one of the world's biggest fashion producers but its fragmented, family-owned industry has not seen consolidation on the same scale as France.
French luxury giant LVMH bought Rome jeweller Bulgari in 2011, while the Qatari royal family outbid Rosso to snap up Valentino for 700 million euros in July.
"It has proved impossible to conglomerate Italy's luxury brands like France did," Umberto Nicodano, partner of Italy-based law firm Bonelli Erede Pappalardo told Reuters.
"The reason: a strong desire of independence of our brands which would have led to issues of governance and valuation."
Marni had long been at the centre of takeover talks.
Castiglioni said they had been approached by equity funds but they decided to partner Rosso because they could keep their identity while pursuing growth on new markets and segments.
"We did not want to have partners for the short term and we hate the kind of pressure that comes from financial markets," Castiglioni, who is chief executive of Marni, said.
The partners attended the conference on Thursday with their respective children, a sign of the importance of family succession in the tight-knit Italian industry.
($1=0.7542 euro) (Reporting by Antonella Ciancio; Editing by Mike Nesbit and Elaine Hardcastle)