Dozens of Conservative MPs have written to the prime minister, Theresa May, urging her to shift billions of pounds of post-Brexit farm subsidies towards protecting and improving the environment.

The 36 MPs, including former environment ministers, also urge May to maintain the strong protection for wildlife and water provided by EU directives. During the EU referendum campaign, farming minister George Eustice campaigned for the leave camp and said the directives were “spirit-crushing” and “would go”.

UK farmers receive about £3bn a year via the EU’s common agricultural policy (CAP), much of it for simply owning land. The Tory MPs want May to “take advantage of the repatriation of CAP by shifting subsidies in favour of paying farmers for delivering services for the environment and public good”.

The development of a new subsidy scheme is seen as one of the most difficult post-Brexit challenges and is now the responsibility of the environment secretary, Andrea Leadsom, a prominent leave campaigner.

In August, the National Trust, a major landowner, called for complete reform of the British farm subsidy system to only reward farmers who improve the environment and help wildlife. The National Farmers Union criticised the plan, saying food production is vital. In July, a large group of 84 political and civil society organisations said post-Brexit subsidies paid to farmers must be linked closely to environmental responsibilities.

The Tory MPs who signed the letter include former environment ministers Caroline Spelman and Richard Benyon, the current chair of the environment, food and rural affairs select committee, Neil Parish, and Zac Goldsmith, member of the environmental audit select committee.

“Done properly, Brexit is a massive opportunity for our environment,” said Goldsmith. “We are urging the PM to put existing EU environmental protections into British law and to honour the green manifesto commitments we made before the election in full. But more than that, Brexit allows us to repatriate and reform the environmentally disastrous CAP to make sure farm subsidies are there to pay for environmental and public services. The upside is enormous.”

An overwhelming majority of the British public wants new post-Brexit laws protecting wildlife and the countryside to be at least as strong as the EU rules currently in place, according to a national opinion poll published in August.

Since she became prime minister, May’s government has banned polluting plastic microbeads from some personal hygiene products but also expanded the controversial badger cull, which leading experts say “flies in the face of scientific evidence”.

It has also backed direct compensation to people in areas affected by fracking and abolished the Department of Energy and Climate Change, with its responsibilities taken up by an enlarged business department. On Monday, Labour offered to work across party lines to enable the UK to rapidly follow the lead of the US and China in agreeing to ratify the Paris agreement on climate change.

The Tory MPs’ letter emphasises the green achievements of previous Conservative governments, including the Clean Air Act in 1956, the creation of the environment department in 1970 and the Wildlife and Countryside Act in 1981. “Integral to Conservative philosophy is a deep cultural commitment to handing on a better world to our children,” it says.

“Lady Margaret Thatcher was always clear that we hold the earth on a full repairing lease,” said Sam Barker, director of the Conservative Environment Network, which co-ordinated the letter. “Theresa May will have a similarly bold vision for how Britain will fulfil the terms of that lease, at home and around the world. We look forward to her setting it out in due course.”

The Tory MPs also urge May to “reaffirm our manifesto commitment to creating a blue belt of protected waters around the UK’s 14 Overseas Territories, including as a first step around the Pitcairn Islands and Ascension Island”. The letter says this would “amount to the single biggest conservation measure of any government, ever”.

The Conservative MPs who signed the letter are: Zac Goldsmith, Richard Benyon, Alex Chalk, Andrew Mitchell, Anne Main, Ben Howlett, Bernard Jenkin, Caroline Spelman, Charlotte Leslie, Cheryl Gillan, David Warburton, Derek Thomas, Flick Drummond, Heidi Allen, James Gray, Jason McCartney, Jeremy Lefroy, Jo Churchill, Kevin Hollinrake, Kit Malthouse, Marcus Fysh, Maria Caulfield, Matthew Offord, Neil Carmichael, Neil Parish, Nicolas Soames, Oliver Colvile, Paul Scully, Peter Bottomley, Richard Graham, Sarah Wollaston, Scott Mann, Stephen Hammond, Tania Mathias, Victoria Borwick, Will Quince.