A major incident has been declared in Bournemouth after thousands of people descended on the area's beaches as temperatures soared.
Council leaders say the numbers of people flooding the seaside in the last two days are "like those seen on a bank holiday".
People are being told to stay away, with dispersal orders issued on beach piers, overnight campers evicted and additional police patrols brought in.
Bournemouth, Christchurch and Poole Council said people had "defied advice to stay away" and condemned them as "irresponsible" as services struggle to cope.
Visitors swarmed to Britain's beaches as the country sweltered in its two hottest days of the year so far, peaking at 32.6C (90.68F) yesterday and 33.3C (91.94F) today, both recorded at Heathrow Airport.
It follows calls for people to maintain social distancing as a further 149 coronavirus-related deaths were reported in the UK on Thursday, bringing the total deaths to 43,230, according to Department of Health figures.
After 10pm, there are still many people gathered on Bournemouth beach.
Sky's Sam Holder said some people have been gathering in groups of 20 to 30, and there is now a sense amongst locals "that they fear that this could be the start of a second wave and that the people of Bournemouth will suffer as a result".
The influx of beachgoers has caused "widespread" problems with illegal parking, "excessive" littering, gridlock on roads and anti-social behaviour, Bournemouth Council said.
There were a number of reported incidents of fights and excessive alcohol use, while cleaning crews received "abuse and intimidation" as they attempted to empty overflowing bins on the seafront.
Along the full stretch of coastline, 33 tonnes of waste were cleaned up on Thursday morning, in addition to eight tonnes collected between the piers on Wednesday.
The council said it has issued 558 parking fines - its highest number on record - and responded to numerous reports of parked cars causing an obstruction.
Roads in and out of the area remained heavily congested into the early hours of this morning.
Tobias Ellwood, Conservative MP for Bournemouth East, warned the gridlocked roads are "hindering emergency vehicles" and said he requested extra police officers for the area if needed.
Bournemouth, Christchurch and Poole Council leader Vikki Slade said: "We are absolutely appalled at the scenes witnessed on our beaches, particularly at Bournemouth and Sandbanks, in the last 24-48 hours.
She added: "The numbers of people descending down here are like those seen on a bank holiday... PLEASE do not come."
Ms Slade later told Sky News: "I think... social distancing is probably long gone. It's much worse than that.
"Thousands of cars abandoned, cars parked on a roundabout to avoid fines, people urinating in other people's gardens, groups of drunk, not in control of themselves."
Conor Burns, MP for Bournemouth West, said the crowds on Wednesday were "the worst I've ever seen it", adding: "This cannot go on."
A multi-agency emergency response is now co-ordinating resources across the area to tackle the issues, with additional police patrols, security in place to protect refuse workers and additional parking enforcement.
Dorset Police has urged people to "think twice" before heading to the area and said the number of visitors has caused a "significant increase in demand" for its services.
Anna Harvey, who chairs Dorset Police Federation, went to Bournemouth beach on Thursday to check on colleagues and provide supplies and water.
"Dorset Police - and our colleagues on the ground - are doing the best they can in these very difficult and extreme circumstances. It's 5pm now and people are still arriving despite the requests to stay away," she said.
"I am afraid people were asked by the government to show common sense and at times there has not been much evidence of that being on display. We are still in the middle of a pandemic."
Rick Da Costa, general manager of NEO restaurant in Bournemouth, described the scenes as "absolutely chaotic".
"While we appreciate the tourism and we appreciate the custom... everyone's just coming here and not really caring about the social distancing," he said.
Some of those visiting said they were not too concerned about people keeping their distance, or felt that people were still sticking to the rules.
Rick, Arun and Idris, who visited from Osterley in west London, said they felt "relaxed" although there were so many people on the beach "they looked like ants" from above.
"To be honest we aren't worried about social distancing. I think that everyone's eased up a bit. You can see it's crowded and that everyone has relaxed about it," said Arun.
Olivia, who visited from Basingstoke, said she felt that "people know to keep their distance".
But Adam and Courtenay, who have lived in Bournemouth since December, said they were "worried" there were too many people.
"We came at 7pm because we hoped it would be less crowded. To be honest, I was hoping it wouldn't be like this," said Adam.
Dorset is not the only area which has struggled to deal with unruly visitors. On Wednesday evening, police were called to a mass brawl involving a crowd of youths at the seafront in Exmouth, Devon.
Many also flocked to parks across the UK, with some people complaining social distancing was not being adhered to.
In Ogmore-by-Sea in Wales, large groups were seen as fights appeared to break out between youths.