Hundreds of pink and purple jellyfish have been spotted on sands at the coastal resorts during the past 48-hours, the latest in a string of sightings this summer.

Experts say it could all be down to warmer weather.

During the past 30 years, there has been an increase in jellyfish in the North Sea and more are expected in UK waters because of climate change.

In the past few years the Marine Conservation Society (MCS) Jellyfish Survey, launched in 2003, has recorded some unusual mass appearances or blooms as the creatures mature and become visible in large numbers at the same time.

Last summer there were many reports of the usually rare dangerous Portuguese Man of War jellyfish washing up on beaches in Devon and Cornwall.

In November there was a "vast and unseasonal bloom" of the mauve stinger jellyfish along Britain's north west coast which severely affected salmon farms off Northern Ireland and the west coast of Scotland.

Peter Richardson, MCS biodiversity programme manager, said: "We're not sure if the mauve stinger bloom was a one-off event, but scientists are predicting that climate change will result in more jellyfish in UK waters and the MCS jellyfish survey aims to record these unusual blooms if they happen again."

He said warmer waters caused by climate change were encouraging the jellyfish, while overfishing was also helping boost numbers.

He added: "As ever, we are encouraging holidaymakers to take part in our national jellyfish survey, but the key message is look, don't touch."

In the UK, the jellyfish season started in April in the Irish Sea, when harmless barrel jellyfish were spotted off the Welsh coast.

There were blooms of moon jellyfish, which are also harmless, around the UK from May and in June and July large numbers of the blue and compass species, which can deliver mild stings, began to wash up on beaches.

To take part in the Marine Conservation Society survey visit www.mcsuk.org