"Obviously only some street police staff are aware of this ... To fund this, police have to find it within their existing budget meaning some services to the public may be affected."
There are 12,000 constabulary and non-sworn police employees.
Fiona Michel, deputy chief executive of people at Police National Headquarters could not say how many were affected or exactly how much they were owed.
"It is too early to confirm the exact numbers of staff affected, the range of payments to be made or the total sum to be paid to current and/or former staff," she said.
"Our first priority is to inform those affected staff of their entitlements before other parties. Police can confirm that the historic issues involve a significant amount of staff and money. However, to put the issue into context, the remediation total will be less than one fortnightly pay run."
On average a fortnightly pay run for police is $40 million, a PNHQ spokeswoman confirmed.
Mrs Michel said the blunder was discovered during a review of the police payroll system last year. She said that review "highlighted a number of issues which, over time, have resulted in staff receiving incorrect payments".
"The issues relate to entitlements under the Holidays Act 2003," she explained.
"The specific areas that require remediation date back to 2009, and are primarily related to the payment of statutory holidays, and the rate of payment for annual, sick and bereavement leave."
She said the money owed had been accrued over two financial years and would be paid back as soon as possible. Police were "committed to doing the right thing" by staff, she said.
"Police informed all staff and the police unions earlier this year that we had begun a pay remediation process. A dedicated project team is working to recalculate pay for a number of current and former employees so that staff will receive their entitlements as soon as possible."
She said once the calculations were completed staff would be advised of the "next steps".
They were most recently updated last month.
"The issues are complex and have taken some time to resolve as we need to ensure that our calculations are as accurate as possible. We need to get this right for our staff, while ensuring compliance with the Act in the future."
Police Minister Michael Woodhouse would not be interviewed on the issue today.
But a spokeswoman said the minister had been given an assurance from police that it could be handled without affecting frontline services.
Police were working with the Police Association, a union representing police staff.
"The Police Association understand that this issue is complex and are appreciative of police's robust and thorough approach to the remediation for current and former members.
Association president Greg O'Connor was aware of the issue.
"We are satisfied that police have made every effort to ensure that the remediation exercise is as thorough as it can be."
