A stunned beachgoer had to tread carefully after finding an enormous one metre-wide jellyfish on a British coastline.

The huge barrel jellyfish washed up in Portland, Dorset, this week, and is thought to be one of the biggest of its kind to ever appear on British shores, British media reported.

Warmer-than-average weather which is expected in Britain in the next few weeks could bring more of the super-sized sea creatures.

Ms Suzanne Sheldon, 48, found the jellyfish when she was walking her dog.

"It was at least 3 foot in width and was very bulky too. It was the largest jellyfish I have ever seen," she said, according to ITV.com.

Richard Harrington from the Marine Conservation Society said: "This predicted hot weather to come, can mean that even more jellyfish are likely to wash up or be in the seas around places like the west-country.

"Although this species is harmless their numbers are likely to grow fairly quickly as sea temperatures rise. We are very keen to hear from people that find any washed up anywhere around the country.

"This is an Atlantic species and are sometimes found washed up but still advise the public not to touch them."