Cases of fatal mouth rot have risen sharply in young harbour seals along the east coast.

Sally Butler, chairwoman of the charity Friends of Horsey Seals, said it had euthanised 25 pups suffering from the condition this year.

She added the animals were already declining in the area and feared the outbreak could threaten their survival.

Sally Butler, chairwoman of Friends of Horsey Seals (Image: Friends of Horsey Seals)

"It's a distinct possibility," she said. "It's going to have a huge affect on their numbers without a doubt.

"It's not just the ones we've euthanised, the British Divers Marine Life Rescue (BDMLR) have euthanised far more than us."

Miss Butler said she believed the young seals were susceptible to the infection because their immune systems were weak.

Norfolk is home to two seal populations: harbour, or common, seals and greys, which are more numerous.

While mouth rot does not appear to affect the larger grey seals off Norfolk's coast,........

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