TOKYO (Reuters) - Artisan Partners, an investor in Japanese retail giant Seven & i Holdings, called on the company's special committee to consider a formal bidding process of competing takeover proposals to secure the highest offer.

Seven & i received a buyout proposal from a member of its founding Ito family, it said on Wednesday, a potential $58 billion white-knight bid as it weighs a rival offer from Canada's Alimentation Couche-Tard.

In a statement, Artisan portfolio manager Ben Herrick said the fund supports both offers at this stage.