Why is the EPA, not the Department of Environment and Conservation (DECC), the prosecutor?
The EPA is a body created by the Protection of the Environment Administration Act, and has various powers and functions conferred on it by that Act, including the power to prosecute. The DECC is the government department that employs staff but section 217 of the POEO Act provides that bodies who can take proceedings for breaches of the Act are the EPA or the other appropriate regulatory authority for that activity.