A mass of stinking seaweed the size of Jamaica is heading to Mexico's most popular tourist beaches, ruining the usually pristine waters for holidaymakers.

The giant floating mass of sargassum algae, more than 340-miles long, is predicted to hit Mexico’s Caribbean shoreline this week, reaching the Yucatan peninsula's coast and spreading as far south as Belize.

Mexico's beaches, in particular Cancun and Tulum, are popular among British tourists looking for a cheap break with warm weather and crystal clear waters.

The sargassum has been affecting some of Mexico's most popular beaches since 2011, but the arrival of the seaweed island, dubbed the "Sargasso stain", in the next few days is a worrying escalation.

The massive explosion of algae has been caused by widespread deforestation in the Amazon and the intensive use of fertilisers which have fed nitrogen into the oceans.