Norwegian energy company Equinor has been granted environmental approval to drill an oil exploration well in the Great Australian Bight, the decision hailed by the federal government and the energy sector but decried by environment activists.

The National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) says Equinor now has two of the four approvals required before activity can begin.

“The rigorous assessment process undertaken by NOPSEMA took almost eight months and involved a range of specialists with considerable environmental, scientific and engineering experience,” the regulator said in a statement on Wednesday.

Equinor was first granted a petroleum title over areas in the Bight in 2011 and now has an accepted environment plan.

It must still have a well operations plan and a facility safety case approved before it can begin drilling its proposed Stromlo-1 well at a site about 400km off the South Australian coast in water more than 2.2 kilometres deep.

If approved, Equinor plans to begin work in late 2020 with the operations expected to last for 60 days.

Federal Resources Minister Matt Canavan said the Bight project had the potential to open up a major new petroleum basin.

“In a continent as large as ours I hope we can find another oil and gas province to replace the Bass Strait,” he said.

“The Great Australian Bight is relatively unexplored but considered to be highly prospective for petroleum resources, with potential to provide significant economic benefits and help strengthen our fuel security as a nation.”

Equinor’s country manager for Australia, Jone Stangeland, said environmental approval was an important milestone for the drilling program.

“We have been preparing for safe operations for two and a half years, holding over 400 meetings with more than 200 organisations across Southern Australia,” he said.

“We will continue to engage with the community as we progress through the process.”

The Australian Petroleum and Exploration Association said it was important for oil exploration to resume in the Bight to understand the scale of the resources and whether commercial development was possible.

“This is an important step towards understanding the energy resource potential of the Great Australian Bight and delivering major economic and energy benefits to the state and the nation,” director Matthew Doman said.

But environmental groups have accused NOPSEMA of ignoring the concerns of the Australian community, coastal councils, experts and tradition owners.

“We are gobsmacked that NOPSEMA could approve Equinor’s plan that experts have slammed,” Wilderness Society Director Peter Owen said.

“The vast majority of Australians don’t want oil drilling in the Great Australian Bight, and we will now be looking at our legal options.

“The fight for the Bight is one of the biggest environmental protests Australia has seen, and this approval will only further mobilise community opposition.”

NOPSEMA said it had imposed stringent conditions on its approval to ensure a high level of protection to the environment, in recognition of the Bight’s unique values and sensitivities.

Restrictions include limits on the time of year any activity can take place, regular public reporting on the impact to the environment andan insistence that additional rigs capable of drilling relief wells in the event of an emergency be in local waters ahead of the project’s start.

-AAP