The NFU and WWF have jointly urged political leaders to safeguard British farmers from food imports that would be illegal to produce in the UK.
The letter asks the Conservatives, Labour and Liberal Democrats to make a manifesto commitment to the formation of a core standards commission.
This would look at the practicalities and legal requirements to ensure imported food meets the same environmental and animal welfare standards as those adhered to by UK farmers.
The joint letter between the NFU and WWF comes as the government continues to open up the UK market to agri-food imports from across the world.
Recently, the UK’s membership of the CPTPP trade deal cleared its final hurdle before being ratified, and the government launched trade talks with Turkey.
NFU President Tom Bradshaw said the letter with the environmental charity "represents the strength and breadth of feeling on this issue."
"It must meet the same production standards as asked of our farmers. It is what the British people expect and its time a system of core standards was properly established in UK law," he said.
“A commission able to develop these core standards is the first real step to making core standards a workable reality.”
Tanya Steele, chief executive of WWF, said the three parties must commit to a commission to establish core standards in trade.
She said: "Farmers and businesses would welcome this and there is clear support from the public to stop fuelling the destruction of nature.
“By setting core standards we would uphold our national climate and nature targets, reduce our contribution to the destruction of nature, and create a level playing field for UK farmers working hard to produce food to higher standards.
“There is no time to lose if we are to secure a resilient and nature-rich future for food and farming in the UK.”
The NFU’s food standards petition, signed by more than 1 million people, calls on the government to ensure all UK food imports match the standards of production that British producers must follow.
