A volunteer group has criticised jet-skiers for “harassing” a group of seals close to the shoreline, where the animals are trying to keep warm while their new coats grow.

Friends of Horsey Seals received a report of two jet-skis hurtling past around 200 grey seals at Horsey Beach in Norfolk on Monday afternoon, panicking the marine mammals.

They said many of the spooked seals stampeded into the sea and that, around 20 minutes later, the jet-skis returned and went through the group of seals in the water.

A couple walking on the beach, who witnessed the incident, took photographs and sent them to Friends of Horsey Seals.

At this time of year grey seals come ashore to moult off their old worn-out coats, the group said.

Their metabolism slows down during the moult and they do not eat as much, staying out of the cold sea to retain body heat until their new coat has grown.

Peter Ansell, chairman of Friends of Horsey Seals, said: “It is common sense that there should be a minimum distance that jet-skiers can come to any beach not only to protect wildlife but also swimmers, especially children.

“Harassing the seals in this way was a dangerous and unacceptable thing to do”.

Sally Butler, a member of the Friends of Horsey Seals Rescue Team, said: “It is vitally important that they keep warm during this six-week process.

“Their condition will deteriorate if they are chased around and are forced to use excess energy.

“Forcing them into the sea at this time can be damaging to their overall health and impact their long-term chances of survival.

“More importantly when the grey seal’s annual moult ends in the next few weeks, the common seal’s pupping season begins, and many heavily pregnant common seals will come ashore and rest among the grey seals.

“Disturbing them at this time risks them aborting their pups.”

Norfolk Police said it had received a report of jet-skis being used in the water near the seals at Horsey, and that inquiries are ongoing.