Thames Water has been hit with a £220,000 fine for polluting a river in Surrey.
It was found guilty of breaching its environment permit by allowing “partially treated sewage and an illegal storm discharge” to enter the River Blackwater in September 2012.
The pollution killed a “significant number” of fish, the Environment Agency said.
Andrew Valantine, Senior Environment Agency officer added: “We take these types of incidents very seriously and will do everything within our powers to safeguard the environment and people affected and that includes bringing those who harm the environment to account for their actions.”
A spokesperson from Thames Water said: “We very much regret this incident and have reviewed procedures and invested in new equipment at the treatment works to reduce the chance of anything like this happening again.”