In a joint letter, Helena Dollimore, the MP for Hastings, Rye, and Chris Corrigan, the CEO of the Sussex Wildlife Trust, urged the EA to treat the incident with “the utmost severity”, taking into account the “devastating impact of the incident on local wildlife and protected habitats”.
Dollimore said: “It is only right that the EA has escalated this incident to the most serious level.
“Southern Water has a responsibility to make amends to our community for this incident and clean up their own mess.
“They made a commitment to fund a programme of nature restoration in our beautiful area, and I will hold them to that promise.”
A spokesperson for Southern Water said: “We are fully cooperating with regulatory investigations and keeping both regulators and stakeholders updated.”
The MP has also launched a petition to end the use of plastic beads in wastewater treatment.