Seiont, Gwyrfai and Llyfni Angling Society take legal steps at Llyn Padarn
An angling society is taking legal steps in a bid to prevent what it says is an environmental disaster at a lake.
Fish Legal has served a notice on the Environment Agency on behalf of Gwynedd-based Seiont, Gwyrfai, Llyfni Angling Society over Llyn Padarn in Llanberis, Snowdonia.
It claims the rare arctic char may die out at the site within 10 years.
The Environment Agency says it is investigating and will take appropriate action based on its investigation.
The Seiont, Gwyrfai and Llyfni Angling Society says sewage pollution has spoiled fishing and is threatening the future of rare arctic char.
Latest figures suggest the char could die out at Llyn Padarn in between five and 10 years.
The society is so concerned it has instructed Fish Legal (formerly the Anglers' Conservation Association) to look at the legality of the situation with the Environment Agency Wales.
In a letter to the Environment Agency, Fish Legal, says the angling society has been "expressing concern" about the sewage discharges into Llyn Padarn since the early 1990s.
By now the situation is so bad that the damage to the lake is threatening the future of a rare fish which lives there, it adds.
"This disaster not only affects the environment, it also will in time affect the local economy and tourism," it says.
Fish Legal is using the Environmental Damage (Prevention and Remediation) (Wales) Regulations 2009 to try and get the Environment Agency to act.
As well as the Environment Agency, it also wants to see Dwr Cymru Welsh Water - as the company which operates a lakeside sewage plant - to take action.
The situation at the lake has been investigated by BBC Radio Cymru's Manylu programme which presents its findings in a programme on Monday.
An Environment Agency Wales spokesman said: "We are investigating a complaint (by Fish Legal) of alleged damage under the Environmental Damage Regulations and will take the appropriate action based on our investigation."
Manylu is on BBC Radio Cymru at 18:03 GMT on Monday.