Russell George, Montgomeryshire AM, said traffic in connection with the Garreg Lwyd wind farm development will cause hold-ups for holidaymakers from Shropshire and Powys.
Mr George said he has sought assurances from the Welsh Government that movements of infrastructure associated with the wind farm development would take place at times of least disruption to residents and outside peak times for visitors to Mid Wales.
However, in spite of previous assurances from the First Minister, Carwyn Jones, that disruption would be kept to a minimum, the Welsh Government's Department for Transport are planning to allow abnormal loads during late summer, in spite of the moratorium which exists for traffic works during the busy summer months.
Mr George said: "I am deeply concerned by the inevitable traffic chaos that will be caused in Mid Wales as a result of the movement of large turbine components for the Garreg Lwyd wind farm.
"In spite of assurances to the contrary from the First Minister, the Welsh Government is preparing to allow movements of abnormal indivisible loads during late summer. I'm further concerned that police resources will be stretched at this busy time.
"These abnormal loads will travel along the A483, and travel along Pool road, over the Kerry road roundabout, and up Llanidloes road. The abnormal loads will then be required to travel under Nantoer bridge on the A489. This particular bridge is also well known for large vehicles having difficulty passing under and blocking the main trunk road."
The developers say there will be regular passing points and delays of just 10 minutes.