Hong Kong investment firm Fung Brands has bought 80 percent of French fashion house Sonia Rykiel in a partnership aimed at boosting the brand's global presence, the companies said on Monday.

Nathalie et Sonia Rykiel.

"The partners want to develop the company as a true international luxury brand," they said in a joint statement.

The Rykiel family will retain a 20 percent stake and the founder's daughter, Nathalie Rykiel, will remain vice president of the board, it said.

Known for its knitwear and founded in 1968, Sonia Rykiel was one of the last family controlled French fashion houses.

The company had sought a potential partner since early 2011 but originally intended to sell off only a minority stake.

Financial details were not disclosed.

Fung Brands was started a year ago by the Fung family, the majority shareholder of Hong Kong's Li & Fung Group, and previously acquired majority stakes in French luxury shoemaker Robert Clergerie and Belgian leather goods maker Delvaux.

Fung Brands director Jean-Marc Loubier said he hoped to double Sonia Rykiel's sales in the next five to six years after the brand saw sales stagnate in 2011 after chalking up 90 million euros ($119 million) in 2010.

The company makes half its sales abroad and distributes its products in 30 countries.