"Guerrilla pumpkin-carvers" in Machynlleth made their opposition to Tesco clear last November
A protest march is being staged later in opposition to plans for a new Tesco store in the Upper Swansea Valley.
Ystradgynlais and District Action Group said there should be a detailed study to see whether the supermarket was needed.
Tesco announced plans to create 180 jobs in the town in January, and also intends to build four other new stores in Powys.
The company said it had received "wide ranging support" from the community.
Last November, campaigners in Machynlleth carved "No Tesco" in pumpkins in a protest against the supermarket chain's plans to build a new store in the town.
In Ystradgynlais, the action group claimed research carried out on behalf of the grocery giant was "deliberately vague" to allow Tesco to draw any conclusions that supported its application.
It said this had angered residents and small businesses in the town.
A spokesman said: "It's one thing to ask somebody where they shop, but quite another if you ask them if they want a huge superstore on their doorstep.
"When a development is likely to have this amount of impact on an area, whether good or bad, it is beyond contempt that they can treat the residents of the Upper Swansea Valley with so little regard.
"Powys County Council should reject the application until they provide a detailed study to establish whether there is a need for this store. We maintain that there is not a need."
Following the protest march at 1815 GMT there will be a public meeting at Ystradgynlais Miners' Welfare Hall.
Tesco said it recently held a public exhibition and many people supported the proposal.
A spokesman said: "From the open public exhibition people voted in favour two to one.
"We understand the concerns of communities on any regeneration plans.
"We will create 180 guaranteed local new jobs and more with a new business park.
"We are in continuous consultation with the local community on these issues and we have received wide ranging support."