The GMB union said that many of the strikers earn little more than the national minimum wage of£5.35 an hour, before bonuses.
GMB members at the retailer's Wigan warehouse walked out this morning (November 9). The workers will mount picket lines throughout the day - and outside JJB sports shops across England and Scotland on Saturday - striking for 24 hours, the third time in two weeks.
Union negotiators are seeking a higher basic rate of pay for staff and are calling for equal access to a bonus scheme.
GMB officials have also complained that employment agencies illegally supplied staff during last week's strike.
Regional secretary Paul McCarthy said: 'GMB members know full well that JJB is collaborating with a range of employment agencies to illegally break the strike. GMB intend to mount a vigorous campaign to expose these illegal plans.'
The union plans to install cameras on each picket line to collect evidence that is admissible in court, if it decides to prosecute the employment agencies.
JJB has 430 shops in the UK. Executive director David Whelan, who also owns Wigan Athletic Football Club, revealed today (November 9) that he is selling another chunk of his 39 per cent stake in the sports chain, for£2 million. The company said Whelan is using the money to pay a tax bill in January.
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