For almost 20 years, NI Water has been protected from the severest pollution fines because of a special arrangement that acknowledges its outdated and underfunded infrastructure.
In March, Environment Minister Andrew Muir said reforms could see NI Water face tougher punishments for issues in the waterways.
Last month Muir introduced a new bill to increase fines and penalties for pollution offences, external.
This will have to go through Stormont’s legislative process before becoming law.
Meanwhile the latest fish kill figures have led to fresh calls for stronger deterrents to stop water pollution.
James Orr from Friends of the Earth said 50,000 dead fish was “not a trivial amount”.
“It’s not just the fish,” he said.
“What are the kingfishers going to eat? What are the otters going to eat, what about the insects which are the building blocks of our rivers?
“They’re all impacted and it’s a national disgrace.”
He suggested the low prosecution rate “encourages polluting by not having successful deterrents”.
“The government needs to stand up to these polluters to protect our water,” he said.
