The federal government is braced for a flood of court cases challenging decisions made under its environmental laws.

Internal Environment Department documents highlight a "marked increase" in cases brought against it since 2011-12 and warn of worse to come.

The department says litigation against high-profile environmental decisions made under the controversial Environmental Protection and Biodiversity Conservation (EPBC) Act, is one of the biggest risks facing the department.

The briefing says there was a spike in "requests for explanations" for EPBC decisions, which are often precursors to court cases, in late 2013 and early 2014.

The department is currently fighting 16 cases in the courts but received 52 requests for reasons, relating to just 17 decisions, between November 2013 and the beginning of April.

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It could even find itself in multiple court actions for the same decision, against a mining company unhappy with restrictions placed on its new project and at the same time being sued by environmental activists saying the conditions are not strict enough.

Environment's internal strategic review is frank in its assessment of the amount of time, and taxpayers' money, it expects to spend in court in the coming months and years.

"The key litigation risk areas for the department relate to challenges by community and interest groups to high-profile environmental decisions made under the Environmental Protection and Biodiversity Conservation Act," the document states.

"The department expects to receive more claims against it in the near future.

"Between November 2013 [and] January 2014, the department received a high number of requests for statements of reasons for various EPBC Act decisions, which often precede a party commencing legal action.

"An increase in claims may contribute to cost overruns for 2013-14."

In one such high-profile case, the department is being taken to the Federal Court by a Queensland conservation group trying to use the EPBC to overturn Environment Minister Greg Hunt's approval of dredging and dumping in the Great Barrier Reef World Heritage Area for the contentious Abbot Point coal port.

A spokeswoman for the department said legal action might come from any of a diverse group of interested parties in big or small environmental decisions.

"Requests [for reasons] were received from proponents, environmental non-government organisations, individuals, businesses and interest groups," she said.

The department also said it was being sued in a number of different forums.

"Of the 16 legal claims, four have been filed with the Administrative Appeals Tribunal, 10 have been filed with various registries of the Federal Court of Australia, including one in the full court, and two have been filed with the High Court of Australia," the spokeswoman said in her statement.

But the Environment Department's top public servants in Canberra believe the Abbott government's environmental policies will fundamentally change their role in approvals processes and potentially limit their exposure to legal action.

The government is looking to sign deals with the states that would establish a "one-stop shop" for environmental approvals, sidelining the EPBC Act, which has been on the books since the Howard government.

"The one-stop-shop reforms will fundamentally change the role of the Commonwealth and the department in the area of environmental regulation," the strategic review states.

"The scale of change may not be apparent until the finalisation of agreements with states and territories. However, reductions in the current assessment and approvals function have been anticipated."