A major offshore oil and gas hub in the Northern Territory has been cleared to operate a second time without an environmental impact assessment.

The federal government has given the controversial $130 million Port Melville on the Tiwi Islands the go-ahead again, with fewer conditions than were set after a review earlier this year.

The deep sea development, 120km north of Darwin, began operating last year without any formal environmental approvals and was waved through by former federal environment minister Greg Hunt.

The Federal Court overturned that decision in October, but Mr Hunt’s successor Josh Frydenberg has now granted approval again without any special operating conditions.

David Morris of the Environmental Defenders Office NT says it makes a mockery of Australia’s environmental protection laws and sets a dangerous precedent.

“It’s a fairly reckless decision to make. You’re talking about storing 30 million litres of diesel in an area that’s subject to frequent cyclones and a high tidal range,” he said.

In November, the company more than halved the number of ships the port will use per year from 480 to 233.

Mr Morris admits that does reduce harms to dolphins, whales, dugongs and turtles in the area from boat grounding.

“But you still have all of the risks associated with a heavy industrial port, an oil and gas hub located in very close proximity to a near pristine environment which is habitat for 38 threatened species – some of which are critically endangered,” he said.

Such a reduction in the intensity and scale of the project must also be of grave concern to investors of the Singapore-based company, Ezion Offshore Logistics Hub, Mr Morris said.

A spokesman for Mr Frydenberg said the marine supply base is not likely to have a significant impact on the environment.

The Environmental Defenders Office is seeking a copy of the reasons underpinning Mr Frydenberg’s “woeful” decision and will determine whether there’s grounds to appeal it.