Environmentalists have protested outside a new incinerator near Gloucester after Council figures revealed it was more than £100 million over budget.
Dozens of people gathered at Javelin Park near junction 12 of the M5 causing traffic jams around the site.
Campaigners say the incinerator is already out of date, and argue there are cleaner ways to deal with waste in the county.
Last month Gloucestershire County Council revealed the project's cost had risen from £500m to more than £600 million.
Campaigners say they had to fight to get the figures released.
The County Council denies that it has not been fully transparent about the figures, and adds the incinerator will generate electricity and save taxpayers money.
The plant was built to save money by burning waste which the authority said represented "value for money" as it was almost 20% cheaper than sending it to landfill.
Council leader Mark Hawthorne says the project have come in over budget because of delays, materials costs, and increased labour prices.