The company has revealed team members who were underpaid are expected to receive their first interim back payments before Christmas.

But they have not yet informed the affected staff.

Woolworths has revealed the issue affected salaried staff, with repayments expected to cost up to $300 million.

A review which commenced earlier this year highlighted an inconsistency in pay for a number of salaried store team members to team members paid under the new Enterprise Agreement.

"Annual salaries for store team members are set to cover ordinary working hours and reasonable overtime," the company said in a statement.

"However, team members are entitled to be paid the higher of their contractual salary entitlements, or what they otherwise would have earned for actual hours worked under the General Retail Industry Award (GRIA).

"The review has found the number of hours worked and when they were worked were not adequately factored into the individual salary settings for some salaried store team members."

Affected current and former salaried team members will receive their full entitlements, including bank payments with interest and superannuation contributions, as soon as possible.

"Interim back payments will be made before Christmas to affected supermarkets and metro salaried store team members for the two years reviewed to date (September 2017 - August 2019)," the statement said.

Woolworths Group chief executive officer Brad Banducci apologised to affected staff.

"As a business we pride ourselves on putting our team first, and in this case we have let them down," Mr Banducci said.

"We unreservedly apologise. The highest priority for Woolworths Group right now is to address this issue and to ensure that it doesn't happen again."

Almost 20,000 team members working for Woolworths are paid an annual salary.

The full review is expected to continue until the end of the financial year.

The company has set up a website for former salaried team members to access further information and provide updated contact details to ensure the Woolworths Group team can get in touch if they are affected.

Former staff members are encouraged to visit team.woolworths.com.au

An internal website has been established with information for current salaried team members.

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