The UK will not weaken environmental or animal welfare standards to secure a trade deal with the US after Brexit, Michael Gove has insisted.
In comments after his first keynote speech as Environment Secretary, Mr Gove said new trade deals must not come at the risk of dropping environmental protections.
In a wide-ranging speech at WWF's Living Planet Centre in Woking, Mr Gove said he "deeply regrets" Donald Trump's approach to the Paris Agreement on climate change, which the US president has announced he will pull out of.
"International co-operation to deal with climate change is critical if we're to safeguard our planet's future, and the world's second-biggest generator of carbon emissions can't simply walk out of the room when the heat is on," he said.
Casting himself as an environmentalist for emotional reasons as well as "hard calculation" about the importance of protecting nature, he promised the audience of environmental and countryside groups a "green Brexit".
"Leaving the EU gives us a once-in-a-lifetime opportunity to reform how we manage agriculture and fisheries, how we care for our land, our rivers and our seas, how we recast our ambition for our country's environment, and the planet.
"In short, it means delivering a green Brexit."
He said farming subsidies in the future would not simply pay for the amount of land farmed but also to deliver environmental benefits including planting trees and protecting treasured landscapes such as the Lake District.
The UK would be a global leader in environmental policy, developing "gold standard policies" on everything from pesticides to animal welfare, he added.
Asked whether striking a trade deal with the US could weaken those standards, he said: "I don't think we should compromise on environmental standards, or sustainability, or animal welfare, in pursuing freer trade.
"The future of Britain in trading terms is not taking part in a race to the bottom. It's competing in terms of quality.
"Of course it is important we explore new trading opportunities, not just with the US, but with other nations across the world.
"But it must not be, and my Cabinet colleagues are agreed on this, at the risk of dropping any environmental standards or protections we currently enjoy."
Concerns have been raised that desperation for a trade deal with the US could open domestic markets to lower standards such as chickens washed in chlorine and beef treated with hormones.
Environmentalists also fear for EU regulation on the environment, amid calls in some quarters to cut "red tape" on everything from energy efficiency to protecting habitats.
They have warned that the process of transferring rules to UK law must not weaken them, but Mr Gove's speech took pains to reassure them Brexit will be a force for good.
He said leaving the EU would allow the UK to take back control of policies governing agriculture and fisheries.
"Informed by rigorous scientific analysis, we can develop global gold standard policies on pesticides and chemicals, habitat management and biodiversity, animal welfare and biosecurity, soil protection and river management and so many other areas."
He also raised the prospect that the UK could support EU moves to tighten the ban on "neonicotinoid" pesticides which have been linked to declines in bees, to cover all crops, after scientific research raised more concerns about their use.
He said he would not make a definitive decision until he had looked more closely at the science and spoken to colleagues.