Supermarket giant Woolworths says it underpaid 5,700 staff by as much as $300 million over nine years.

"Woolworths Group unreservedly apologises after a review found that approximately 5,700 salaried store team members... have not been paid in full compliance with Woolworths Group’s obligations under the General Retail Industry Award (GRIA)," a spokesperson said in a statement.

In the video above, Marley Spoon secures funding from Woolworths

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

CEO speaks out

Woolworths Group CEO Brad Banducci admitted to reporters the company has let their employees down.

“As a business, we pride ourselves on putting our team first, and in this case, we have let them down. 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.”