Beachgoers have been blamed for the deaths of three seal pups in three days.
The Friends of Horsey Seals said one of the animals drowned on Sunday after being chased into the water, while another was abandoned by its mother after being surrounded by people.
A third died after being attacked by a dog two days earlier.
The charity said deaths due to "human intervention" were "not acceptable" and urged visitors to keep their distance.
A spokesman said in one case on Sunday "two young children were allowed by their mother to chase the young unweaned, non-waterproof pup into the water where it drowned".
Another seal pup died on the beach at Winterton, Norfolk, after its mother was unable to reach it after it was surrounded by visitors, he said.
Prof Ben Garrod, from the University of East Anglia, said: "The action of visitors to Horsey and Winterton are killing seals. Actually killing them.
"The vast majority of people are amazing it's just a handful of absolute idiots. It is a criminal offence to cause death to any protected species."