TOKYO - U.S. fund Artisan Partners urged the board of Seven & i Holdings to allow Canada's Alimentation Couche-Tard (ACT) to conduct due diligence and negotiate a purchase price after its $47 billion bid to take over the Japanese retail company.

In a letter dated Oct. 15, Artisan portfolio managers David Samra and Benjamin Herrick said a restructuring plan announced last week by the 7-Eleven owner - in which it will bundle non-core assets into a holding company - was "too little, too late".

"The price currently being offered by ACT is clearly superior to the speculative value that could potentially be achieved by implementing the restructuring plan at this late date," they said in the letter.

A spokesperson for Seven & i declined to comment publicly on the firm's dealings with individual shareholders or on the status of discussions with Alimentation Couche-Tard.

The Canadian company announced a preliminary bid for Seven & i in August, and sources said last week it has since hiked its offer by 22% to around $47 billion. If the deal goes ahead, it would be the largest-ever overseas buyout of a Japanese firm.

Artisan has been among some of Seven & i's vocal foreign investors who have urged the company to focus on its core convenience store business.

The letter also says Seven & i should make public the names of the members of the special committee that was set up to scrutinise the bid.

Only the chairman of the committee has been disclosed, which "invites suspicion that management-friendly members have been hand-picked to serve on the committee," it said.

Artisan had previously sent a letter to Seven & i in August calling on the firm to consider ACT's initial, lower offer as well as solicit offers for the company's Japanese subsidiaries.

Artisan holds 1.11% of Seven & i's outstanding shares, LSEG data showed.

(Reporting by Anton Bridge and Rocky Swift; Editing by Muralikumar Anantharaman and Edwina Gibbs)