Jair Bolsonaro is transforming Brazil into an “exterminator of the future”, the activist and politician Marina Silva has warned, as she and seven other former environment ministers denounced the far-right president’s assault on rainforest protections.

The eight former ministers – who served governments across the political spectrum over nearly 30 years – warned on Wednesday that Bolsonaro’s government was systematically trying to destroy Brazil’s environmental protection policies.

“We are watching them deconstruct everything we’ve put together,” said José Sarney Filho, who served as environmental minister under the rightwing presidents Fernando Henrique Cardoso and Michel Temer.

“We’re talking about biodiversity, life, forests … the Amazon has an incredibly important role in global warming. It’s the world’s air conditioner; it regulates rain for the entire continent.”

Silva, the environment minister under Luiz Inácio Lula da Silva, said: “What is happening is a dismantling, taking education and the environment and making them ideological issues.”

She said the government risked “transforming our country into the exterminator of the future – and we can’t let that happen”.

Bolsonaro has been severely criticized at home and abroad for his claims that environmental protections hinder Brazil’s economic growth. He is a close ally of the powerful agribusiness lobby and during his campaign said that if he were elected he would not allocate “one more centimeter” of land to indigenous reserves.

Izabella Teixeira, who led Brazil’s negotiating team at the Paris climate agreement as environment minister under the leftwing president Dilma Roussef, said that Bolsonaro’s policies were already damaging the country’s international standing.

She said: “Being a climate-change denier is very serious because it’s a geopolitical issue. The signals the government is now sending against the international consensus is compromising our credibility – not to mention our image.”

In a speech on Wednesday, Bolsonaro said that he would remove environmental protections in a part of the forested coast south of Rio de Janeiro in order to created “a Cancún of Brazil”. Bolsonaro received a $2,500 fine from environment police for illegal fishing in the reserve in 2012.

The ex-ministers highlighted the “depletion” of the environment ministry’s powers, including stripping it of jurisdiction over the country’s water agency and forestry service and also eliminating three senior officials, including the secretary on climate change.

Bolsonaro’s administration has also transferred the authority to allocate new indigenous lands from the indigenous affairs agency to the agriculture ministry. At one point Bolsonaro was considering withdrawing from the Paris agreement.

“The environment defenders have their hands tied and the worst actors – the polluters, the agribusiness – have a pistol in theirs,” said Carlos Minc, environment minister under Lula. “I’d say it’s become the ministry of anti-environment.”

Bolsonaro’s environment minister, Ricardo Salles, responded with a statement in which he accused previous administrations of “poor management” and alleged that there was a campaign to besmirch Brazil’s reputation.

“What is damaging Brazil’s image is the permanent and well-orchestrated defamation campaign by NGOs and supposed experts, within and outside of Brazil,” he wrote.

Salles has called climate change a “secondary issue” and said environmental fines were “ideological”. Within his first weeks in office, he issued a three-month suspension on partnerships between the government and NGOs and later called the late revered environmental activist Chico Mendes “irrelevant”.

Earlier this week, Salles canceled a trip to the UK, Norway and Germany. The Folhapress news agency reported that the minister backed out of the trip because of a letter signed by 602 scientists that called for European businesses to only do business with Brazil on the condition it met commitments to reduce deforestation and indigenous conflicts.