Frankfurt - Hugo Boss has signed up designer Jason Wu, a favourite of American First Lady Michelle Obama, as the German fashion house seeks to sell more women's dresses and suits in the United States and China.

Hugo Boss, mainly known for its suits for men, gets about 11 per cent of its 2.4 billion euros (US$3.2 billion) in annual sales from womenswear and has been looking to expand this area.

Taiwan-born Wu, known for his love of ladylike designs, founded his eponymous label in New York in 2007 but rose to fame after designing the ivory one-shoulder gown that Michelle Obama wore to Barack Obama's first inauguration ball in 2009.

He also designed the red dress she wore to Obama's second inauguration ball in February this year.

"I plan to develop a strong, feminine womenswear collection that reciprocates the brand's authority in menswear," he said in a statement on Monday.

Wu, 30, will take on the newly created position of artistic director for Boss Womenswear, with his first collection for the brand to be shown in autumn and a debut runway show during the New York Fashion Week in February 2014.

The group is in negotiations with Womenswear Creative Director Eyan Allen, who has been with the company since 2007, over his future role, a spokeswoman for Hugo Boss told Reuters. Wu's new title is superior to that of Allen's.

Womenswear has so far proven difficult for Hugo Boss, as the market is more crowded than that for men's fashions, HSBC analyst Antoine Belge said.

"Even Hugo Boss has acknowledged that it's not where it wants to be on womenswear. They haven't yet found the right balance between classic and comfortable and more cutting-edge," he told Reuters.

Hugo Boss posted a 5 per cent fall in womenswear sales in the first quarter of 2013, while sales of menswear were down 2 per cent, mainly due to a shift in the number of collections it is producing a year.

"This will generate a powerful and creative statement for Boss Womenswear and show our commitment to focus even more on the female side of the brand," Hugo Boss Chief Executive Claus Dietrich Lahrs said of the appointment.

The appointment of Taiwan-born Wu comes after France's Cacharel signed up Chinese designers Ling Liu and Dawei Sun in 2011. A Hugo Boss spokeswoman said Wu's appointment was not meant to reflect a focus on any market in particular, but that the group was impressed by his international style.

However, Wu is popular in China, a key battleground for luxury clothing brands. Hugo Boss is pushing its presence there through a catwalk show in Shanghai and is opening new flagship stores in Shanghai and Hong Kong.

The announcement also comes on the same day that British handbag designer Mulberry said the creative director behind its famous Alexa and Del ray bags, Emma Hill, had asked to leave the group.