Foul play is suspected after at least three porpoises were found washed up on Sheppey beaches without their fins.

The bodies of two of the mammals were discovered within a few hundred yards of each other at Leysdown last Wednesday morning. Another had been spotted not far away two days earlier.

The latest gruesome discovery was made by Miranda Stephney, of Ann Boleyn Close, Eastchurch, who was walking her dogs.

“They must have been de-finned,” she said.

“It was probably while they were still alive and done out at sea. Then they’re thrown back in and they drown.

“There was another one a couple of days ago seen by my dad. He assumed it was a boating accident because there was only one.

“But when there are three it’s clearly not an accident – plus they’ve lost their side fins as well.”

Miranda’s dad, Mick Kinsey, of Preston Hall Gardens, Warden, added: “I think it’s commercial fishermen killing them.”

He said fishermen saw them as a nuisance because they get caught in their nets, where they are either injured or die; some had even been clubbed to death.

“It’s awful,” he said. “They cut the fins off, pierce their stomachs to let the air out in the hope they will sink to the bottom.”

The carcasses were reported to the RSPCA.

Porpoises are a protected species and have the same protection as dolphins.

Under the Wildlife and Countryside Act 1981, it is illegal to intentionally kill or injure a porpoise and causing them distress in any way, such as chasing them in a boat, is also outlawed.

Swale council officers have seen similar carcasses but believe they had been injured accidentally rather than anything more malicious.

A council spokesman said: “We are aware of these cases, and the ones we’ve come across look like they have received injuries from boats.

“If anyone comes across a dead or stranded mammal on a beach, dial 999 and report it to the coastguard who will investigate and inform relevant organisations.”