A £700m waste management plant on the outskirts of Londonderry could be stalled after Sinn Fein decided to support residents in their opposition campaign.
The SDLP has accused the party of doing a u-turn after backing the plan for the plant in the Executive.
Sinn Fein dismissed this, saying party policy was against incineration.
Construction on the project at Maydown was due to begin in January, but local people and anti-incineration campaigners have mounted a vigorous opposition campaign, claiming proper consultation was not carried out.
Sinn Fein says it agrees with the residents that more research into the long-term effects of the gasification plant needs to be done.
The party also says proper public consultation and notification of planning approval |for the facility was not carried out.
Derry City Council is one of seven councils in the region which will have its waste processed at the 150,000 sq ft site selected for the project.
The opposition campaign |has stepped up a notch with the Foyle Sinn Fein MLA Maeve McLaughlin revealing that the party now opposes the construction after conducting its own research into the plant.
Ms McLaughlin said: “In line with party policy we felt we took the best decision in the interests of the people of Derry and in particular the residents of Strathfoyle and Culmore.
“We also need to take into account the concerns of residents in our neighbouring county of Donegal in areas situated along the River Foyle such as Muff, Moville and Greencastle.
“Whilst some may argue that gasification is the lesser of two evils and whilst some argue that it is not as detrimental to our health and environment none of this can be proven.
“The jury is still out and therefore our position remains one of opposition.
“What we need to do as a city is to present a case for credible alternatives for waste management — a culture of zero waste.
“We fully understand the predicament Derry City Council has been placed in to meet European landfill targets and the potential penalties that may come from this.”
But Derry SDLP Councillor Shaun Gallagher, vice-chairman of the Northern Ireland Executive Waste Programme Board, described the move as ill thought-out and accused Sinn Fein of doing a policy u-turn.
Councillor Gallagher said the current position of Sinn Fein in Derry would have dire consequences for ratepayers and flies in the face of the all-party support already given to the project at every government level.
“We must reach the recycling targets which have been set by Europe otherwise we face daily fines of £500,000 as a region,” Councillor Gallagher warned.
Three groups are behind the plans to build the gasification plant — Derry-based Brickkiln, which specialises in waste management and civil engineering; Sisk, an international construction company; and international waste management business, Shanks.
According to the Brickkiln company website, the plant will handle 120,000 tonnes of waste annually and supply 30 gigawatt hours of renewable electricity to the grid — enough to support the energy needs of 6,000 homes for a year.
It is estimated that the facilities will create 200 construction jobs and a further 40 full-time posts. Opponents claim the long-term effects of the plant have not been fully investigated.