Scotland Yard will demand HM Revenue & Customs foots the record bill for the police force's hunt for the missing data discs containing 25 million child-benefit records.
The Metropolitan Police has said it will seek full costs from HM Revenue & Customs (HMRC) for what is being reported as the most expensive lost-property inquiry in the UK.
The police's search for the two missing CDs is being "wound down", with reports that officers are no longer searching premises and think the discs will probably never be found.
A spokesman for the Metropolitan Police said: "We will be seeking full recovery of the cost of the investigation. The investigation is being wound down but it is not concluded."
The Metropolitan Police would not confirm the exact cost of the investigation but an article in The Daily Telegraph claimed the investigation has cost tens of thousands of pounds, quoting a source at Scotland Yard as saying it had demanded more resources "than you would see used in a major murder investigation".
The HMRC has previously guaranteed to cover the "incremental" costs of the police investigation, such as overtime, accommodation and travel expenses.
A spokeswoman for HMRC said the department has agreed to pay the costs that "we have triggered as a result of the police investigation into the disappearance of the child-benefit data".
At the investigation's peak, 47 detectives from the Specialist and Economic Crime Command were charged with searching for the two CDs that went missing in October last year after a junior official at HMRC sent them unrecorded in the post to the National Audit Office (NAO).
Police are reported to have searched NAO offices, two HMRC premises and other government buildings, the Royal Mail depot in Belfast, four TNT depots and a rubbish tip in Kent, with the main search concluding on 5 December, 2007.
Michael Upton, spokesman for the Metropolitan Police Authority, said the matter could be raised at the authority's next meeting.
Upton said: "If there are particularly large costs, we might ask whether they are proportionate and whether everything was done to ensure as effective value for money as possible."
The password-protected CDs contain the names, addresses, dates of birth and national insurance numbers of the entire HMRC child-benefit database. They also include the bank account details of more than seven million parents, guardians and carers.
No banks have reported any unusual activity in the affected accounts to date.
A separate inquiry into how the data went missing is being conducted by the Independent Police Complaints Commission.