Exclusive: Charity World Vision Australia underpaid staff

One of Australia's biggest charities has admitted to underpaying staff.

9News has revealed World Vision Australia reported itself to the Fair Work Ombudsman in December.

The charity has confirmed it owes 200 casuals and 45 permanent staff members money, and has set aside $8.9 million to pay them back.

World Vision Australia Acting Chief Executive Officer Graham Strong, said the underpayments were caused by an error in determining the correct award for employees.

"We apologise unreservedly for the error and have moved swiftly and decisively to rectify it," he said.

A statement from a Fair Work spokesperson said the Ombudsman "is aware of alleged underpayments and is conducting inquiries in relation to World Vision".

"Any workers with concerns about their pay should contact us directly," it said.

Australian Services Union Branch Secretary Matt Norrey said the ASU expected World Vision to rectify the underpayments "as a matter of urgency".

"The ASU is extremely disappointed that yet another underpayment of employees has occurred in an ever-growing list of employers," he said.

Coles, Woolworths, the ABC and Red Cross Australia are among other employers who have admitted to underpaying staff.