Newcastle United owner Mike Ashley has bought almost 56.8m shares in department store Debenhams.
Ashley's Sports Direct business has purchased almost 5% of the company, which is said to be worth around £46m.
"This acquisition of shares has taken place without the prior knowledge of the Debenhams board of directors," The Mirror quotes a Sports Direct statement as saying.
"But Sports Direct has communicated to Debenhams' board its desire to work together and its intention to be a supportive shareholder."
Ashley set up Sports Direct shortly after leaving school in 1982.