Ms Reeves said that in some cases – where other inheritance tax relief also applies – the APR threshold could in practice be around £3m, meaning it only targets the wealthiest landowners.

But farming unions in Wales dispute this, arguing that many smaller family farms will be affected by the changes.

Mr Jones said: “The changes announced are not only a threat to the fabric of our family farms and our tenant sector, but also to our nation’s food security.”

Bernard Llewellyn, a farmer from Carmarthenshire, said another effect of the change could be that land sold to pay the tax was “taken over by companies across the border” to plant trees and “mitigate carbon emissions “.

This would be in place of “land used by a young farming family to produce food that is desperately needed in this country,” he said.

Kate Miles, manager of the agricultural mental health charity DPJ Foundation, said the organization had been contacted by farmers who were deeply concerned about the situation.

“We’re seeing this level of fear, concern and outrage across the country … a very powerful maelstrom of emotions that is having a serious negative impact on mental health,” she said.