More than 240 conservation scientists have called on Scott Morrison to drop his opposition to stronger environment laws and seize a “once-in-a-decade opportunity” to fix a system that is failing to stem a worsening extinction crisis.

With the federal government due to this week announce a 10-yearly legislated review of the Environmental Protection and Biodiversity Conservation (EPBC) Act, the scientists have signed an open letter to the prime minister urging him to increase spending and back laws to help protect the natural world from further destruction.

The letter says three native species have become extinct in the past decade and another 17 could follow in the next 20 years. More than 1,800 Australian plants and animals are formally listed as threatened with extinction, but the scientists say this is an underestimate.

“Our current laws are failing because they are too weak, have inadequate review and approval processes, and are not overseen by an effective compliance regime,” the scientists say.

“Since they were established (in 1999), 7.7m hectares of threatened species habitat has been destroyed. That’s an area larger than Tasmania. Meanwhile, the number of extinctions continue to climb, while new threats emerge and spread unchecked.”

Environmental law was a point of difference at this year’s election, with Morrison pledging to limit “green tape” that he said cost jobs while Labor promised a new environment act and a federal environment protection authority.

Lesley Hughes, a distinguished professor of biology at Macquarie University, member of the Wentworth Group of Concerned Scientists and a signatory to the letter, said environmental protections had been consistently wound back over the past decade, most often by conservative governments.

She said it was having a significant impact, pointing to the 2016 state-of-the-environment report that found Australia was facing multiple environment changes and lacked a national policy that established a clear vision for the protection and sustainable management of the country’s natural heritage.

She also cited a WWF assessment that ranked eastern Australia as one of the world’s top 11 deforestation hotspots. Australia was the only developed country on the list.

“It’s a very grim picture,” Hughes said. “This letter is a pre-emptive strike to say this is an opportunity to do it better, this is not an opportunity to weaken and dilute the existing weak laws.”

Morrison’s pledge not to increase environmental laws came as a United Nations global assessment found biodiversity was declining at an unprecedented rate, with one million species across the globe at risk of extinction and human populations in jeopardy if the trajectory was not reversed.

The environment minister, Sussan Ley, said the review of the EPBC Act was an independent process that would encourage submissions from a wide variety of perspectives.

She said the government was investing significantly in environmental restoration and land care programs to promote biodiversity and safe havens for native species. She announced the Indigenous protected area network, areas of land and sea owned or managed by Aboriginal and Torres Strait Islander groups, would be expanded by 28% to more than 100m hectares, an area similar to the size of South Australia.

A Guardian investigation last year found most campaigners and political veterans believed environmental protection was now harder to win in Australia than at any time since before the wave of landmark 1980s decisions to save Tasmania’s Franklin River, recognise the Daintree rainforest and Kakadu national park and to block mining in Antarctica.

Less than 40% of nationally-listed threatened species had recovery plans in place to secure their long-term survival. The federal environment department admitted earlier this year it did not know whether the recovery plans that were in place were being implemented. Conservation groups found spending on the environment department has been cut by nearly 40% since the Coalition was elected in 2013.

The review of the EPBC Act will be held against a backdrop of escalating land-clearing, particularly in Queensland and New South Wales. Business groups have regularly called for the environmental approval process to be simplified to stop delays to major projects.

The scientists’ letter was organised by the Australian Conservation Foundation and is backed by the the Places You Love Alliance, a collection of 57 organisations including BirdLife Australia, Humane Society International and WWF Australia. The letter calls for laws that “safeguard our intact ecosystems and protect the critical areas people and wildlife need to survive”.

Suzanne Milthorpe, nature campaign manager with the Wilderness Society, urged the government to use the review to upgrade the EPBC Act from a piece of legislation that catalogued the loss of nature into one that helps prevent it.

“Extinction is a choice,” she said.