June 10 (Reuters) - Frasers Group ( SDIPF ), the retailer controlled by British billionaire Mike Ashley, launched a €2 billion ($2.31 billion) takeover offer for struggling German fashion brand Hugo Boss on Wednesday.

Frasers ( SDIPF ), the biggest shareholder in Hugo Boss with a 26.06% stake, is offering €38 per share in cash for the remaining shares - a 4.3% premium to the €36.44 closing price of Hugo Boss stock on Wednesday.

Hugo Boss would be the latest addition to Ashley's sprawling retail empire, which includes Sports Direct and House of Fraser under Frasers Group ( SDIPF ), as well as stakes held by Frasers ( SDIPF ) in Asos, Debenhams, and Currys.

Hugo Boss has been struggling with falling sales and set out a new strategy six months ago to revamp stores, streamline its product range and offer more womenswear. Its shares are trading at around half their value three years ago.

"To facilitate further investment by Frasers ( SDIPF ) in Hugo Boss, Frasers ( SDIPF ) has decided to make a voluntary public takeover offer to all Hugo Boss shareholders for all Hugo Boss shares not directly held by Frasers ( SDIPF )," Frasers ( SDIPF ) said in a statement.

Hugo Boss said late on Wednesday that Frasers ( SDIPF ) did not coordinate the takeover approach with the company and that its board would review the offer, which values the remaining shares, representing 73.94% of the company, at about €1.98 billion.

Frasers ( SDIPF ) said it remains supportive of Hugo Boss CEO Daniel Grieder and Chairman Stephan Sturm - a reversal after saying in November that it no longer had confidence in the latter. 

It said Frasers ( SDIPF ) CEO Michael Murray, who also sits on the supervisory board of Hugo Boss, did not participate in the board's discussion or decision to make the offer. 

Ashley, who holds 73.7% of Frasers Group ( SDIPF ), stepped down from the board in 2022, and handed the CEO role to Murray - his son-in-law.

BNP Paribas and Deutsche Bank were financial advisers to Frasers ( SDIPF ) on the offer.

($1 = 0.8654 euros)