James Evans says the health board has made the “wrong decision” in pushing ahead with temporary changes to Minor Injury Units and ward-based services in the county.
The Brecon and Radnorshire MS said it was “a sad day for everyone in Powys.”
They also agreed a temporary change to the clinical model for inpatient care in Brecon, Bronllys, Llanidloes and Newtown.
The proposals will be introduced on a temporary basis for a six-month period.
Both changes are expected to be in place by December.
Reacting to the news, Mr Evans said: “I had hoped the board members would have recognised the difficulties residents already have in accessing healthcare and oppose these plans, especially as some of them have spent many years campaigning for better healthcare services, but sadly they did not.
“The board should be listening to the needs and the very real concerns of residents, many of whom put ideas forward at the public meetings on how to increase services and improve efficiencies in the area - but today's meeting just shows they are not listening.
“PTHB say they will monitor the effectiveness of the changes during this 'temporary' period of change, but it is not clear how they intend do this, what measures they will use or how they will know how many people cannot access a specific service.”
Mr Evans also said the health board needs to take “a long hard look” at its management structure.
“The Health Board still have a major budget deficit to resolve and yet within the past week the Health Board have advertised for an Assistant Director of Transformation & Value on £71k+ and a Deputy Director of Allied Health Professionals on £84k+,” he said.
“They need to ensure that every post is providing taxpayers with value for money, and work towards increasing frontline services rather than reducing them.”