The PSNI and Dalradian Gold are understood to have called in lawyers after clashing on the issue of security costs at the latter’s Tyrone mine.
It was revealed in August that policing the gold mine had already cost tax payers around £500k.
But at the time, a spokesperson for Dalradian told the Mail the PSNI had ruled security at the site was necessary.
The PSNI has since billed Dalradian £400k for the cost of escorting explosives to the premises, but the amount remains unpaid.
Chief Constable George Hamilton told the Irish News: “To date a total of £397,000 has been invoiced, however Dalradian are in disagreement with the chief constable’s position on cost recovery.
“Both parties are seeking further legal advice and this matter is with PSNI’s legal counsel. No monies have been received to date.”
A spokeswoman for Dalradian Gold said: “There is a legal requirement in Northern Ireland for the PSNI to assess the need to escort the transportation of explosives. The form and manner of the escort is determined solely by the PSNI.
“We understand no other mining or quarrying operation in Northern Ireland pays for this service.
“Total investment into the project over the lifetime of the mine is expected to be in excess of hundreds of millions of pounds, creating hundreds of jobs in the process.”
Dalradian intends to submit an planning application for a full gold mine and processing site in Greencastle this Autumn.
Many locals remain opposed to the mine because of health and environmental concerns, but Dalradian insist the use of cyanide on the site will be heavily regulated.