The data, if supplied, would have detailed a log of serious incidents at the facility including assaults, self-harm and major disturbances. The request took in a period of nine months from August 2015, following the period covered by the Nauru Files published by Guardian Australia last year.

"This assessment is made considering the nature of the information and the current nature and extent of the department's relationship with Nauru."

"It is the view of the relevant business area of the department that releasing the information . . . would adversely impact the ability of the department to maintain good working relations with the government of Nauru.

"In consulting this particular FOI request with the government of Nauru, it requested that any reference to Nauru be exempted from release," the department advised.

The decision is a departure from the department's previous determination to release incident logs from Nauru, including detailed summaries, in response to a Fairfax Media FOI request in 2015. That data, published in January last year, revealed self-harm was at epidemic levels at Australia's offshore facilities in Nauru and Manus Island, including multiple cases of asylum seekers swallowing shampoo, slicing themselves with razor blades and dousing their bodies in boiling water.

In a letter, FOI officer Joshua Hutton of the DIBP referred to the Australian Information Commissioner's guidelines, which state that information may be redacted if there is a possibility for "intangible damage, such as loss of trust and confidence in the Australian government or one of its agencies" to arise from publication.

Information relating to three incidents at the Nauru facility was released as it was already in the public domain. The department also released selective and highly-redacted records from the Manus Island detention centre.

The standard time frame for processing FOI requests is 30 days. The department delayed its determination several times in the eight months since the request was lodged in June. In August, FOI officer Brad Collins informed Fairfax Media the department would refund the costs of the FOI application because it had failed to process the request within the statutory guidelines.

A internal memo accidentally copied to Guardian Australia in October revealed the immigration department had been "freezing" FOI requests related to Nauru. In the email to colleagues, FOI assistant director Ian Campbell expressed concern and suggested "releasing the documents sooner, with the Nauru information fully exempted under grounds of international relations".