Sue Essex ruled out revoking planning permission

They claim the plans to burn domestic waste at the plant will release cancer-causing chemicals into the air, damaging local people's health.

The issue is potentially explosive close to the 27 September by-election in the Swansea East constituency.

The campaign group had intended to field an election candidate, but did not submit a nomination, claiming the fight would distract from the incinerator issue.

Around 16 protestors blockaded the site and one hung from a makeshift scaffold at the entrance to the site.

The proposed incinerator is to take municipal waste from nearby Neath Port Talbot and Bridgend.

Welsh Environment Minister Sue Essex did little to take the heat out of the controversy last week when a spokesperson said she would consider requests to call in the site's planning permission, which had already been granted.

The following day, Ms Essex ruled out revoking the permission.

Incinerator arguments

Mike Ryan of the Stop The Incinerator campaign said: "It's absolutely disgusting how they are endangering the public in general.

"It's been so hush-hush and nobody is getting the full story."

The campaigners held a sit-in protest at the Environment Agency offices in Swansea when the body said there appeared no reason not to grant a licence to the development.

But Antonio Pereira, site manager from HLC which will run the plant, was quick to refute the criticism.

"I am sure that if there is anything dangerous to health in the area, we would not have got permission to build the plant," he said.