Hundreds of angry protesters stepped up the campaign against plans to build a 30-mile long high-voltage power line in parts of Shropshire and Mid Wales with a march in Welshpool.
About 300 people carried banners and placards and marched along the high street yesterday.
Click here for more photos from the protest march
National Grid has said it wants to install a 400,000-volt line from a substation in Cefn Coch, near Llanfair Caereinion, to a cable in Lower Frankton near Oswestry.
It will link wind farms in Mid Wales to England's national power network.
The firm had arranged a meeting with Powys councillors about the scheme yesterday, ahead of a public debate on the proposals.
Protesters, who were not allowed inside the private meeting, organised the gathering via e-mail, Facebook, word-of-mouth and the Montgomeryshire Against Pylons website.
They met at 4pm yesterday and marched to the council offices with passing drivers honking their horns.
Hundreds of people lined the entrance road at Neuadd Maldwyn, forcing councillors to walk past protesters.
One of the organisers, Alison Davies, said she was encouraged by the number of people who turned up. "We will continue to fight. We are very angry," she said.
Another organiser Tudor Jones added: "There are people here from all over the area. It will be peaceful but National Grid know our condemnation of the proposals."