The decision by the Welsh government means that tough new rules will be brought in over how farmers deal the manure from their livestock.
Russell George, Member of the Senedd for Montgomeryshire said: "It is incredibly disappointing that Wales is to transition to a nitrate vulnerable zone covering the whole of the country from April 1, a decision which is a kick in the teeth for the Welsh farming sector when it least needs it.
"Given that we’re 10 months into a pandemic, a crisis that has had a dramatic effect on all sectors of business including farming, I'm astonished that the Environment Minister has decided to take these steps now, hitting farmers when they’re down, especially given the fact she had previously said she wouldn’t look at doing this while we were still going through the pandemic.
"Time and time again, the Welsh Government has taken a blanket approach to a problem, forcing everyone to suffer. This time it is farmers who are going to endure the Welsh Government’s inability to deal – in a proportionate way – with what the farming industry acknowledges is a problem.
"There is real despair within our rural communities at the lack of understanding by the Welsh Government of issues outside Cardiff. The Minister must reverse this decision immediately, or face alienating further still Montgomeryshire's farmers. If my Party forms the next Welsh Government following the Senedd elections, we have committed to reversing this decision, a commitment which I welcome."