The government will move to reassure the public that Britain’s current high standards on animal welfare and farming will be maintained after Brexit with a pledge to ensure future trade deals live up to the values of farmers and consumers.

“Our strong British food brand is built on the high standards to which we hold ourselves,” Theresa Villiers, the environment secretary, will tell the Oxford Farming Conference on Wednesday. “We can maintain and indeed enhance UK standards as we negotiate new trading relationships with friends and neighbours in the EU and leading global economies.”

However, Villiers is expected to stop short of promises on specific standards, such as chlorinated chicken and hormone-fed beef, and her choice of words – such as “can” instead of “will” – leaves room for interpretation. Farmers and campaigners want to see more specific promises enshrined in law.

Minette Batters, the president of the National Farmers’ Union, called for the government to bring in a new food standards commission with the power to scrutinise potential trade deals and ensure they prevent imports of food that would be illegal for farmers to produce in the UK.

“British farmers are world leading in our standards of animal welfare, environmental protection and food safety,” she said. “Farmers and the public want it to stay that way.”

Rob Percival, the head of food and health policy at the Soil Association, said: “The government’s stated commitment to protecting the UK’s farming standards post-Brexit is welcome, but needs to be embedded in legislation. If the government is truly committed to ensuring that trade deals live up to the values of farmers and citizens, they should have no objection to providing reassurance by legislating in the agriculture bill to guarantee this.”

Trade experts have warned for years that governments such as the US will demand access to UK markets for their food exports, which are often produced to vastly different standards than under EU rules, as the price of any trade deal. For instance, chicken dipped in chlorine is legal in the US but experts say it opens the way to food-borne illness, and standards on antibiotic use in farming are stricter in the EU than in most other countries.

The question of whether standards could be sacrificed to seal trade deals is vital not just to many consumers, but to farmers who fear a flood of cheap imports that will undercut their products with lower-quality goods, and the closure of EU markets to UK exports if domestic standards are lowered.

Villiers will also pledge to bring forward the long-awaited agriculture bill, the biggest shake-up of British farming in four decades, this month. The legislation was delayed by Brexit, and will change the subsidies given to farmers, which are based mainly on the amount of land farmed, so they are rewarded for protecting the environment, though full details on how this will work have yet to be laid out. There will be a seven-year period of adjustment before the changes are fully implemented.

Current farming subsidies, amounting to about £3bn a year, are to be maintained throughout the current parliament, the government has said.

Batters also urged ministers to come forward with plans for achieving net-zero carbon for the agriculture sector. “British farming could achieve net zero by 2040 [10 years sooner than the government’s pledge for the whole country],” she said.

“The defining factor to reach our goal and help tackle climate change is a willing government. We are already leading the way in producing climate-friendly food in this country, and this government has a chance to enshrine the UK as a global leader in sustainability.”