Sports Direct bought the stores from JJB over a two-year period
Sports Direct's purchase of 31 stores from rival JJB is to be investigated by the Competition Commission.
The Office of Fair Trading referred the deal to the commission after Sports Direct failed to sell stores in five areas with competition concerns.
Sports Direct had been warned in May that it faced an inquiry if it failed to find buyers for the outlets.
The OFT said Sports Direct had not sold the stores and had "made no significant progress in doing so".
"The OFT does not believe that Sports Direct would be able to arrange sales to suitable buyers, even if given a reasonable period of additional time. As such, it is now appropriate to refer the case to the Competition Commission," the OFT said.
Sports Direct - which is controlled by Newcastle United owner Mike Ashley - owns Sports World and Lillywhites stores. It bought the 31 stores from JJB over a two-year period.
Sports Direct declined to comment on the OFT's move.