The federal government has been accused of "over-enthusiasm" in redacting documents filed in court in the case of a Tamil family fighting deportation.

Sri Lankan couple Priya and Nades and their Australian-born daughters Kopika and Tharunicaa, aged about five and three, are detained on Christmas Island ahead of a Federal Court challenge due to begin on Friday.

Priya, Nades and Kopika have already been refused refugee status and the court fight hinges on Tharunicaa and her right to apply for protection.

AAP

In a pre-hearing matter on Monday, Justice Mark Mochinsky said he had begun to read documents filed on behalf of Immigration Minister Peter Dutton.

"There does seem to have been some over-enthusiasm with the redactions," he said.

The issue was raised by Tharunicaa's lawyer, Angel Aleksov, who noted issues with redactions to two documents he received late Sunday night.

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One document was a ministry briefing between the Immigration Department Secretary and Mr Dutton from mid-July last year.

The other was a document "wholly blacked out" which he said appeared to involve some engagement between Australia and Sri Lanka.

He requested until Monday afternoon to raise the issue with the minister's legal team.

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Justice Mochinsky also noted concerns that the surnames of people within the department had been redacted.

"I was having a little trouble piecing together who was who," he said.

He's asked that all documents be handed to the court without any redactions on Friday so if issues are raised during the hearing they can be dealt with on the spot.

The hearing is scheduled for two days, but Mr Aleksov said he expects it will realistically take only one.

The parties are due to return to court at 3pm on Monday if the redaction issue cannot be resolved.