Plastic pebbles caused by seaside barbecues are threatening to choke Britain’s beaches, environmental campaigners have warned.

Experts in Cornwall said they are monitoring reports of an increase in so-called “plastiglomerates”, created from melted plastic combined with other matter such as sand, shingle or seaweed, washing up on the coast.

The bodies are thought to originate from plastic bottles and similar items melting after being thrown on beach bonfires and barbecues.

The Cornish Plastic Pollution Coalition warned that by the time the plastic particles have been rolled along the beach by waves, they are difficult to distinguish from natural pebbles.

The organisation cautioned people to stop melting plastic on beaches, saying it has seen reports of hundreds of plastic pebbles being found in Cornwall, Devon, Pembrokeshire, Orkney, Spain, Portugal and Hawaii.

CPCA, a spokeswoman, told the BBC: "The danger is that they will become shingle-size and be ingested into the food chain, so they need to be removed like any plastic would be.

"But if people are aware of them we should find more.

"Cornwall gets hit because of currents coming across the Atlantic and if you are a seasoned beachcomber your eyes get attuned to spotting them."