NUREMBERG, Germany (Reuters) - Adidas (>> adidas AG) is proposing that Egyptian tycoon Nassef Sawiris and a representative of Belgium's richest man Albert Frere join its supervisory board after both took significant stakes in the German sportswear group.

Some investors have said the Adidas board, dominated by German consultants and union representatives, lacks the clout of its rival Nike (>> Nike Inc), whose board of directors includes heavyweights such as Apple (>> Apple Inc.) chief executive Tim Cook.

Adidas said on Wednesday the supervisory board was proposing that Sawiris and Ian Gallienne, the head of Frere's holding company Groupe Bruxelles Lambert (>> Bruxelles Lambert), be elected at the company's May 12 annual general meeting for a three-year term.

"The two candidates not only share our view on the growth prospects for the group, but will also bring a wealth of international experience as well as extensive financial and entrepreneurial expertise to the board," Chairman Igor Landau said.

Sawiris and Frere have both taken stakes of more than 5 percent in the world's second biggest sportswear firm in the last year.

Adidas shares, which are up almost 11 percent this year, closed down 2 percent, underperforming a flat German blue-chip index <.GDAXI>.

The company is due to present full-year results on Thursday, although it has already reported provisional figures that beat forecasts.

Reuters reported in December that Sawiris had formed a partnership with U.S. investor Mason Hawkins to spur boardroom change and influence strategy at companies they invest in, including Adidas. Hawkins owns 3 percent of Adidas.

Southeastern Concentrated Value, the entity combining the interests of Hawkins and Sawiris, welcomed the appointments to the Adidas board.

"These additions will bring true shareholder representation to the company and will further enhance the industrial expertise of the board," Scott Cobb, managing partner of Southeastern Concentrated Value, said in a statement.

"We have known Nassef Sawiris for many years and believe that his industrial expertise and capital allocation prowess are an invaluable addition to the Adidas supervisory board."

Adidas announced in January that Henkel's (>> Henkel AG & Co KGaA) Kasper Rorsted would take over as its new chief executive in October, succeeding Herbert Hainer, who headed the firm for 15 years as the longest-serving boss of a leading German company.

There has been speculation that Hainer might be keen to succeed Landau as chairman after a cooling-off period. But many investors are looking for a fresh start under Rorsted, hoping he will cut costs and also consider a disposal of long-struggling fitness label Reebok, which Hainer acquired in 2005.

The supervisory board of Adidas currently has 12 members, and will be increased to 16, with two to be picked by employees in addition to Sawiris and Gallienne, Adidas said.

(Additional reporting by Victoria Bryan in Berlin and Joern Poeltz in Munich; Editing by Georgina Prodhan and Jane Merriman)

By Emma Thomasson