The Wigan-based group confirmed pre-tax losses of 66.5m for the six months to the end of July, compared with £24m during the same period last year.
Like-for-like sales which measures sales in stores open for more than a year also fell by 17.7 per cent with total sales tumbling a fifth to £142.4m.
JJB – which boasts 195 stores and 4,500 employees – identified Christmas, the January sales, the 2012 Games and the European football championships as key shopping periods.
In March of this year, the struggling retailer avoided administration for the second time after landlords and creditors threw their support behind an emergency rescue through a second company voluntary arrangement (CVA.
While the multi-million pound losses have almost tripled, chief executive officer Keith Jones remained optimistic.
He said: "Despite the consumer environment being extremely challenging and expected to remain so for the foreseeable future, our re-sized store portfolio and other cost-saving initiatives have allowed us to manage the business and maintain tight financial controls.
"Our focus on people and processes is yielding early wins and with the continued hard work from colleagues across the Group, I remain confident of JJB's return to profitability and growth.
"Our turnaround plan is now firmly established in the business and good progress has been made in a number of key areas, however there is much still to do."
Jones blamed the closure of unprofitable stores and the sell-out of old and obsolete stock as the main problems behind the balance sheet.
He added: "Despite the tough trading climate, the business is in better shape than of late and has the opportunity to develop the JJB proposition into a truly authentic sports retailer over the next few years."
By Andy Pearce