The PSNI was forced to close roads into Portrush and Portstewart on Sunday after traffic jams formed as hundreds of day-trippers flocked to the seaside resorts to enjoy the Bank Holiday weekend sunshine.
There were also reports that Newcastle in Co Down had also experienced a surge in day trippers heading for a day at the seaside.
SDLP MLA Cara Hunter MLA said residents on the north coast were outraged at the mass of arrivals.
"The influx of cars today in the Causeway Coast is absolutely shameful, with bumper to bumper traffic on Portrush's Main Street," she said.
"We cannot become complacent. Covid-19 is still spreading.
"After speaking with concerned residents, I have contacted police about my great concern for health and safety of local residents here.
"After lockdown we'll be delighted to welcome visitors from across Ireland - but for now stay home and save lives. There will be plenty of time to holiday after this health crisis ends. You are putting lives at risk."
DUP councillor Mark Fielding told the Belfast Telegraph angry residents had been contacting him about the issue.
"I think it's just the bank holiday weekend," he said.
"More people have come here than we thought would have done.
"I think the police dealt with it fairly well."
He said there had been indications earlier this week that young people might be heading to the north coast after lockdown rules began to ease.
But he added: "I don't think it was necessary for so many people to come to Portrush and Portstewart from far away.
"We can't become complacent - we can't let our guard down.
"We want to keep the incidence of Covid-19 low here.
"There's no reason for people to flock to the coast."
A local resident who asked not to be named said police had stationed cars at strategic access points into the town, where they were turning away cars.
"The town was rammed, with big queues at the ice cream creams vans and crowds on the seafront," he said.
"Everyone is really up in arms about it.
"The north coast has been pretty free of Covid-19 , and now all these people are taking the opportunity to drive up here for the day."
The PSNI were approached for comment on this story, but had not responded by time of going to press.