Protestors from Portmarnock dressed as giant turds greeted bemused politicians returning from their summer break at the gates of Dail Eireann on Tuesday.

Portmarnock Drainage Awareness descended on Kildare Street as they lobbied TDs and Senators for their support in objecting to a giant sewage plant in Fingal.

The group is opposed to Irish Water’s plans to build a waste water treatment facility at Clonshaugh with an outfall pipe off the coast near the Baldoyle Estuary.

Earlier this month, the deadline for submissions was extended after key information was omitted from the planning application – and protesters want others to join them.

Lending his support, Fianna Fail TD Darragh O’Brien said building a monster plant to take waste from 500,000 people in the Greater Dublin Area was a flawed concept.

He added: “We know that localised plants work. From a Fianna Fail perspective we are absolutely united in our opposition to this plant.

“Just because we’ve gone down the road of seeking planning for this plant … it’s not too late to stop it.

“This is a plant which will cost over €1 billion that will treat waste to the most basic of standards. It’s not acceptable to our community, absolutely not acceptable.”

Party colleague Deputy Sean Haughey, who has called for an oral hearing on the proposal, said he was very concerned at such a large-scale facility being built on a 43-acre site in “such a densely populated area”.

He added: “I believe Irish Water have shown themselves in recent weeks to be very incompetent and I don’t trust them. Irish Water messed up on the planning application in the first place, they forgot to provide basic information.

“Sewage should be treated as close to the source as possible, so smaller treatment plants around the city would be much more in line with sustainable environmental principles.”

Sea swimmer Catherine Martin said: “Portmarnock beach is a fabulous spot, we were down there this morning. The outfall [pipe] will only be one kilometre to the north of Ireland’s Eye, that is frightening.

“If this goes ahead, it means we won’t be able to swim in the water, we will be swimming in dirty water. They’ve worked so hard to get a Blue Flag, it would be a shame to lose it.”

Protesters also took to the streets in Clonshaugh at the weekend citing odour control, a lack of faith in Irish Water, and a lack of public consultation as their biggest concerns.