The Albanese government has approved an extension to 2070 of one of the world’s biggest gas export projects, saying it has agreed on conditions to protect more than 1 million pieces of ancient world heritage-listed Indigenous rock art that sit nearby.

Climate campaigners have described Woodside’s North West Shelf extension as a “carbon bomb” incompatible with global climate goals. The approval was met with fury from conservation groups and the Greens on Friday, who said it was a “betrayal” of Australians who wanted climate action.

The federal environment minister, Murray Watt, proposed an approval for the Western Australian project in May but his department had since been in talks with Woodside about conditions relating to nitrous oxide emissions. The detail of those conditions was not made public at the time.

The extension allows Woodside to keep operating its Karratha plant, which processes and liquifies gas for export, beyond 2030 and to 2070.

Confirming the approval, Watt said he had imposed 48 conditions on Woodside that related to monitoring and restricting industrial emissions, including nitrous oxide, that could damage the rock art.

“We are confident the conditions we have set are the right ones to protect jobs and economic opportunities and to protect the rock art,” he said.

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He said emissions of gases including nitrous oxides and sulphur dioxide would be capped and then reduced. Nitrogen oxide emissions would need to fall by 60% by 2030 and 90% by 2061, with a similar target for sulphur oxide gases.

The Karratha plant neighbours the Murujuga Indigenous rock art complex – a landscape of more than 1 million petroglyphs dating back 50,000 years, including the oldest known image of a human face.

Critics contest the rock art is being damaged by emissions from the gas plant, but scientists for a state government-backed monitoring program have mostly dismissed those concerns.

The Murujuga complex was described by UN advisers as a “manifestation of creative genius, inscribed in the landscape since deep time” when it was given world heritage status in July after a decades-long campaign by traditional owners.

An aerial view of part of the Murujuga cultural area, where more than 1 million petroglyphs dating back 50,000 years can be found. Photograph: D. Fowler/Fuzz Digital

The federal government led a lobbying effort to overturn recommendations by UN advisers that the nomination should have been sent back to Australia until industrial emissions were stopped.

The minister on Friday also granted a “partial” protection of the site under the Aboriginal and Torres Strait Islander Heritage Protection Act, after an application more than three years ago from traditional owner and Mardathoonera woman Raelene Cooper, of the Save our Songlines group.

Cooper asked the environment minister almost four years ago to make a declaration to protect the site under section 10 of the act. To make a declaration, the minister must be satisfied that the area is significant to Aboriginal people and is “under threat of injury or desecration”.

The declaration says objects in the protected area cannot be moved, damaged, defaced or disturbed, but this excluded any damage from “industrial gaseous emissions”.

Cooper said the decision to extend the project will “hang around Albanese’s neck for the remainder of his leadership”. In a statement released through Save Our Songlines, she said she felt the s.10 decision had been “rushed” out to coincide with the extension, and was “a betrayal of Aboriginal people… a betrayal of all Australians”.

“This is not just destroying Murujuga country, but will impact communities all around the world. It is a shameful act and a shameful decision,” she said.

Cooper said she was seeking further legal advice.

Peter Hicks is the chair of the Murujuga Aboriginal Corporation, a governing body made up of five language groups –the Ngarluma, Yaburara, Mardudhunera (Mardathoonera), Yindjibarndi, and Wong-Goo-Tt-Oo peoples – who act as custodians after the Yaburara people, the artists and traditional owners of Murujuga, were killed or driven off the land in the 1800s. Hicks said the declaration added “a further layer of protection to an area of such great significance to our people”.

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Labor ‘has betrayed Australians’ on climate, critics say

Conservation groups have described the North West Shelf project as the most polluting project in the southern hemisphere, with estimates of total emissions above 4bn tonnes of CO2-equivalent.

Gavan McFadzean, climate program manager at the Australian Conservation Foundation (ACF), said it “beggars belief that the Albanese government would choose to detonate this carbon bomb”.

“With this decision, prime minister Albanese has betrayed Australians who voted for him, believing he was serious about acting on climate change.”

According to Woodside’s own reports, the project extension will be responsible for 87.9m tonnes of CO2-e per year, including the greenhouse gases released when the gas is sold and burned, mostly overseas.

This is the equivalent to about 20% of Australia’s current annual carbon footprint.

Birds on exposed rocks at low tide in the south of Scott Reef. Woodside is aiming to drill for gas around Scott Reef to supply its Karratha plant. Photograph: Wendy Mitchell/Greenpeace

Woodside is working through state and federal approvals to drill for gas in the Browse basin and, controversially, around Scott Reef, that it would use to further supply the now extended Karratha plant.

Woodside’s chief operating officer in Australia, Liz Westcott, welcome the approval and said it “provides certainty for the ongoing operation of the North West Shelf Project, so it can continue to provide reliable energy supplies as it has for more than 40 years”.

Bill Hare, a prominent international climate expert and chief executive of Climate Analytics, said the approval was dangerous and “gaslights the nation, rejects climate science, undermines the ability of the world to achieve the Paris agreement’s 1.5C warming limit, and is a slap in the face of our Pacific island neighbours”.

Hare said the approval could see Australia facing international legal action after an international court of justice advisory earlier this year. That advisory said a state may be committing a “wrongful act” by failing to protect the climate system.

The Australian Greens said the approval was “a betrayal and a disastrous decision for the future of our planet” and had “blown apart Labor’s credibility on protecting our climate and environment”.

David Ritter, chief executive at Greenpeace Australia Pacific, described Woodside’s extension and drilling plans as “grotesque”. Matt Roberts, executive director of the Conservation Council of WA, said there were “no conditions which would make this an acceptable decision”.