The public champion of the world’s largest marine reserve – the Cook Islands’ Marae Moana – has said she lost her job managing it because she supported a moratorium on seabed mining in the Pacific.

Six months ago, Jacqueline Evans won the Goldman Environmental prize – the world’s foremost environmental award – for her work establishing Marae Moana (meaning “sacred ocean”), which covers the Cook Islands’ entire exclusive economic zone of more than 1.9m sq km.

Evans alleges she lost her job as director of Marae Moana because she argued in favour of a 10-year-moratorium on seabed mining to allow for research on its environmental impact.

The Cook Islands government is proceeding with mining exploration, saying it wants to be at “the frontier of the new gold rush” and could be ready to start seabed mining within five years. It says mining the seafloor for metallic nodules could provide financial security for the islands and help them mitigate climate change.

“The catalyst was my policy advice to my colleagues within government that we support Vanuatu, Fiji and PNG on their support for a 10-year moratorium on seabed mining … so that baseline scientific data can be collected,” Evans told Guardian Australia.

She said she was “gravely concerned that government officials don’t want to take the time” to collect data from the reserve, including on the little-understood species that live in the deepest parts of the ocean.

“Our ocean is important to us, for our survival. If we destroy the ocean, we destroy our food supply, our livelihoods and our economy. Marae Moana represents how Pacific Islanders feel about their Pacific Ocean. It’s important that this viewpoint is upheld.”

The proponents of seabed mining argue it can provide minerals critical to renewable energy industries with little waste. But environmentalists arguing for caution say precious little is known about the deep ocean, and even less about the potential environmental impacts of mining it.

Evans was one of six winners of the Goldman prize in 2019 for her “five-year grassroots campaign” to better protect the Cooks’ marine biodiversity.

In addition to mandating sustainable use of its waters, Marae Moana established a 50-nautical mile fishing exclusion zone around each of the Cooks’ 15 islands, leaving those waters exclusively for the use of island communities.

The Cook Islands’ prime minister, Henry Puna, has been crucial in directing government support for the reserve, and the former rugby league player Kevin Iro, now ambassador for Marae Manoa, first proposed the idea and led the campaign for the marine park.

But Evans was responsible for developing government policy and the Marae Moana Act, which parliament passed in 2017. Until last month, she was the sole employee of the Marae Moana Coordination Office.

In a statement reported by the Cook Islands News, the prime minister’s chief of staff, Ben Ponia, thanked Evans for bringing “passion, expertise, and energy into this role”.

Several sources have told the Guardian that Evans lost her job, which was within the office of the prime minister, because of her support for the moratorium. This has been reported in the Cooks, and has not been denied by the government.

The prime minister’s office did not respond to a request for comment on Evans’s dismissal.

Evans said a moratorium should be acceptable to both supporters and opponents of mining.

“Advocates for manganese nodule mining … say that the only life at 4.5km to 6km deep, where the manganese nodules lie on the seabed, are small ‘head lice’,” she said. “We know so little about the ecosystem at that depth. We need to collect more information before such statements can be made.”

The Cook Islands Seabed Minerals Authority said ocean survey work over four decades had identified as much as 12bn square tonnes of mineral-rich manganese nodules spread over the Cook Islands’ continental shelf.

“This seabed mineral resource offers a significant opportunity for the long-term sustainable economic and social development of the Cook Islands,” it said.

In a statement last week, the minerals authority said: “Despite calls for a 10-year moratorium on seabed mining in the Pacific to allow time to conduct more environmental research, the Cooks are set to be the frontier of the new gold rush”.

Deputy prime minister Mark Brown said seabed mining could prove vital to the country’s financial security and contribute revenue towards climate change resilience.

“We can’t just sit back and expect good things to happen for the country, and I see us as taking the lead,” Brown said.

Deep-sea – or seabed – mining has proved contentious wherever it has been proposed.

Proponents argue it could yield ore far superior to land mining in silver, gold, copper, manganese, cobalt and zinc, with little, if any, waste product. The industry is potentially worth billions of dollars and could assist the transition to a renewable energy economy, supplying raw materials for key technologies such as batteries, computers and phones.

Environmental and legal groups have urged extreme caution, arguing there are potentially massive ramifications for the environment and for nearby communities.

Scientists argue deep sea biodiversity and ecosystems remain poorly understood, making it impossible to properly assess the potential impacts of mining – including disturbance of seafloor ecosystems, sediment displacement and noise, vibration and light pollution.