The chief executive of massive retailing conglomerate Wesfarmers has warned against imposing more "punitive penalties" on companies who underpay staff, after the Perth-based group revealed it had underpaid Target staff by $9 million.

When releasing its half-year earnings result on Wednesday morning, Wesfarmers said it had uncovered further payroll errors after discovering underpayments at Bunnings and its industrial and safety division last year.

A total of $9 million in provisions were booked relating to Target staff who had been underpaid by the multibillion-dollar retailer. The company said the cases related to less than 1 per cent of Target staff and revolved around inconsistencies between worked hours and entitlements under the relevant award.

The fresh pay snafu comes months after Wesfarmers revealed it had also underpaid staff at its hardware retailer Bunnings and its industrials companies: Blackwoods, Workwear Group, Coregas and Greencap.