Three documents were withheld despite protest from the nation's information and privacy watchdog, the Office of the Australian Information Commissioner, a leaked letter shows.

Fairfax Tasmania can reveal the program's Stage 2 Annual Progress Report, Stage 3 Mid-Year Progress Report and Stage 4 Annual Progress Report have been barred from release, due to a confidentiality clause signed by the two governments.

The letter, obtained last week, shows an unnamed applicant requested the dossiers from the federal Environment Department in May, under Freedom of Information laws.

The request sparked a legal tussle between the federal Environment Department and Tasmania’s Department of Primary Industries, Parks, Water and Environment.

The letter shows the dossiers were considered for released to the applicant, but DPIPWE intervened, claiming the subject matter was "highly sensitive".

In its response to the federal Environment Department on July 4, DPIPWE argued the release of the information was not in the public interest and would only "contribute to confusion and misinformation" about the controversial FEP.

"The subject of foxes and the eradication program is a highly sensitive matter within the state," the letter reads.

"The information was provided to the (federal Environment) Department (by the state government) on the understanding that it was communicated in confidence.

"Its release could cause damage to the relationship between the Commonwealth and Tasmania."

In writing on July 5, the applicant argued the release of the documents was "unquestionably in the public interest and is a matter of public importance".

"Release of this information promotes effective oversight of public expenditure and transparency in funding acquittals and reporting would mitigate concerns of maladministration and/or fraud in the use of public monies."

Allegations of evidence tampering by members of the FEP are currently being considered by Tasmania Police.

The federal Environment Department's landcare program delivery branch assistant secretary Steve Costello concluded the release of the documents was not in the public interest, stating it was "confidential information".

He declared their release "would not inform debate on matters of public importance".

"The Caring for Our Country Fox Eradication Program... is a joint commitment by Tasmania and the Commonwealth. The program therefore relies on an ongoing sound working relationship between the parties," Mr Costello writes in the letter.

"If the (federal Environment) Department were to disclose Documents 1, 2 and 3, particularly following an objection by the DPIPWE to do so, this could impact adversely on the ongoing working relationship between the Commonwealth and the State Tasmania, both in relation to this program and future bilateral programs."

On Monday, a DPIPWE spokesman said it was the Commonwealth’s decision not to release the information.

But the letter shows the documents will only be released if DPIPWE gives written consent.

cclarke@fairfaxmedia.com.au