After buying Footasylum, the sportswear chain was forced to sell it.
The price it paid for Footasylum was much higher than the one it sold for.
The takeover was stopped by the UK's competition watchdog.
A private equity firm is buying it.
The merger could lead to less choice and a worse deal for customers according to the competition and markets authority.
The Competition and Markets Authority fined Footasylum andJD Sports almost five million dollars for sharing commercially sensitive information. Peter Cowgill resigned from the company after it was fined.
The sharing of commercially sensitive information was accidentally broken.
It said the decision to block the takeover was inexplicable.
According to a report in the Sunday Times, Mr Cowgill was filmed meeting his counterpart at Footasylum, Barry Brown, at a car park in Greater Manchester.
The two bosses failed to alert the regulators after exchanging commercially sensitive information.
Neither man could provide documentation around the meetings, with no notes, no agendas, no emails, and poor phone records, some of which were deleted before they could be given to theCMA.
The regulator was accused of using inflammatory language.
There are 700 stores in the UK and Ireland that sell brands like Nike and Adidas.
Footasylum has more than 65 stores in the UK.
The target audience of the two businesses is slightly younger than that of Footasylum.
Footasylum was founded in 2005 by the co- founder ofJD Sports.