The Farmers Union of Wales has expressed dismay at “the monumental decision” to scrap Tir Mynydd payments.
Gareth Vaughan, FUW president, said there was no doubt that hill farmers would feel betrayed at losing support linked to disadvantages of climate, terrain and topography.
The payments were vital for farmers on the 80% of Welsh land classified as less favoured.
The changes would be studied in detail at meetings of the union’s land use and parliamentary committees.
Dai Davies, NFU Cymru president, said the union must ensure that the proposals were manageable, practical and deliverable at farm level.
“Getting the detail of the scheme right is of paramount importance,” Mr Davies said.
“Unless the basis of the new scheme is sound and fair it will be neither be fit for purpose now or in the future.
“Change invariably involves winners and losers and this could be critical to the viability of some farm businesses.
“It is crucial that there is a managed transition that allows farmers to adjust to the new and different demands now being made upon the industry.”