James Evans has criticised plans from Boots pharmacy in Brecon to discontinue their Sunday rota.
The company has cited “significant inflationary pressures and workforce challenges” as reasons for ending the Sunday service.
Community pharmacies in Wales are allowed to offer prescriptions of medicines for acute illnesses like respiratory infections.
Data from 2021 showed that more than 16,000 patient consultations for prescribing services in community pharmacies in Wales had taken place in the previous four-and-a-half years.
Mr Evans said: “The pharmacy has provided an invaluable service to a wide range of people in the area.
“The negative impact of this closure will be keenly felt, and we desperately need services like this to keep running.
“Pharmacies are an important part of the medical landscape and need proper funding to take pressure off hospitals and GP services.
Boots has been approached by the Brecon & Radnor Express for further comment.