Larne residents have been complaining about a major diesel leak into the sea, and about what is claimed to be a lack of a visible clean up.
Engineering firm Caterpillar has confirmed it was responsible a massive diesel leak in the area at the weekend.
UUP councillor Andrew Wilson said complaints about it had come from those taking part in a boating regatta at Larne harbour at the weekend.
Mr Wilson said: “Local residents have been contacting me because the Northern Ireland Environment Agency (NIEA) have been out taking water samples – but they see no evidence of any clean up operation.
“People do not know who the NIEA are, they do not know how to contact them,
“There are also concerns about the lack of guidance to the public – should they be staying away from beaches?”
He added: “Participants in the East Antrim Boat Regatta in Larne harbour at weekend complained of a rancid smell in the area.”
A Caterpillar spokesman said: “A significant proportion of the diesel was contained on site, however, a quantity had also entered a storm drain.
“We have employed the services of an accredited environmental contractor to assist with the clean-up, and we continue to work closely with the NIEA.
“The safety of our employees and the environment around our facilities is our main priority in this regard.”
A spokesman for NIEA said: “Following a report received via the Water Pollution Hotline on Saturday morning, the Northern Ireland Environment Agency has been investigating a water pollution incident near to the north of Larne Harbour.
“Over the course of last few days, the Agency has investigated and monitored oil ‘sheening’ northwards along the coast from the Harbour as far north as Southtown. From investigations so far, NIEA has confirmed that there has been a significant spill of red diesel into the sea from an industrial premises.”
The spokesman added: “NIEA notified the Maritime and Coastguard Agency, Larne Port, and the local council and is continuing to work with all relevant stakeholders.
“NIEA staff are continuing to assess the impact and will continue to monitor the situation. NIEA has lifted samples and is continuing to gather evidence with a view to taking appropriate enforcement action.”