Hardware giant Bunnings has blamed a coding error in its payroll system for underpaying superannuation to a number of its staff for the past nine years.

The error affects part-time workers in its Australian stores who worked more than their annual contracted hours in the 2011 financial year onwards, which "in most cases" only affected superannuation payments from May or June in the relevant year.

Bunnings has vowed to repay staff within four to six weeks. Credit:Patrick Scala

The Age and The Sydney Morning Herald understands that, excluding compensation, most affected workers are owed less than $200 in unpaid super.

Bunnings would not reveal the full amount it had underpaid its workers, saying it was undertaking a "reconciliation" and would make a back payment plus compensation to affected employees in four to six weeks.