The National Trust is seeking to make half of the food in its cafes either vegan or vegetarian as part of its pledge to become net zero by 2030.
The Trust, which owns 280 historic sites across the country, will ask its 2.6 million members to vote on the controversial proposal.
Currently, about 40% of its catering is plant-based, but the charity is aiming to up this to 50% within two years, if the resolution succeeds.
But NFU president Tom Bradshaw said that visitors to National Trust sites should not have decisions about food 'imposed' on them.
He also said there were benefits to eating meat and dairy. “What we eat is a personal choice and not something which is imposed,” he added.
“Decisions should be made in an informed way taking into consideration the nutritional, environmental and biodiversity benefits that eating a balanced diet including meat and dairy provide.”
North Wales farmer Gareth Wyn Jones added that it was "absolutely ridiculous from a massive landowner with so many livestock farming families living off these farms".
The proposal will be voted on at the National Trust’s annual general meeting in Newcastle on 2 November, with online votes due in by 25 October.
