The UK is facing the threat of a tsunami which is being downplayed, an expert has claimed.
Unstable volcanic land in La Palma, Canary Islands, could trigger an eruption and set off the natural disaster, scientists warn.
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Research suggests a part of land the volume of the Isle of Man could break away from the Spanish island and smash into the Atlantic Ocean.
This could result in a huge tsunami with waves up to three metres high, threatening to swallow coastal towns such as Plymouth.
The looming tsunami would travel faster than a jet aircraft, and would devastate much of southern Britain as well as the eastern seaboard of America, reports Plymouth Herald .
Dr Simon Day, of University College London, said the country needed to prepare for the natural disaster which would wipe out whole towns and travel several miles inland.
"It could be several metres high, it depends where you are and how much energy the wave has," he said.
"If a tsunami of two or three metres hit the south west of England or Ireland you have a lot of tourists on beaches."
While the scientific community is divided on the exact impact of La Palma's collapse, Dr Day believes recent studies have proved him right.
"There was a series of objections," he added. "But independent modelling has shown the same things as me. My response is it's better to know so we can prepare."
Theories surrounding the tsunami date back more than decade. In 2005, a Government report concluded that the risk of a tsunami hitting the region could not be ruled out.
A team from the British Geographic Survey said the tsunami would hit the coast after seven to eight hours, providing plenty of time for warnings.
Three years ago, it was also discussed at an emergency planning conference involving local councils and 999 organisations.
It was initiated by the Devon and Cornwall Local Resilience Forum (LRF), an association of local authorities, agencies and "blue light" services which deals with major events.
Doubts, though, have been cast on the extent of the La Palma collapse, and its consequences.
Professor Iain Stewart, director of the Sustainable Earth Institute at Plymouth University, said: "The volcano collapse is real but the nature of it is strongly contested, and the assumption of the mega-wave is speculative and unlikely, though there are few if any science papers that come out and critically dispute it explicitly.
"There is better evidence of mega tsunamis elsewhere, and the La Palma conjecture certainly spawned a thriving new research field."
Nevertheless, the website TsunamiWatch is calling on authorities like Plymouth City Council to do more to prepare for the natural disaster.
It says that while some areas may have time to evacuate a number of inhabitants to higher land, the majority will not be rescued in time because "the political and civic leaders will not have heeded this warning, or acted soon enough".
"Our minimum target is to get all the warning sirens, used so successfully during the war, replaced and supplemented by extra ones so that everyone in low lying areas within 30 miles of the sea, lesser distances in areas with higher land, can be warned as effectively as possible," says the site.
"This disaster may not happen straight away. It may be twenty, forty, sixty, eighty years ahead, but on the other hand it could be next week. The population will only get one chance to survive."
A spokeswoman for Cornwall Council said it was a member of the Devon, Cornwall and Isles of Scilly Local Resilience Forum (LRF), made up of representatives from emergency services, the police, local councils, the NHS, the Environment Agency and other partners who work together to plan for and respond to emergency situations.
"As part of its work the forum has carried out a detailed assessment into the risk of a tsunami affecting the South West," said the spokeswoman.
"This found that, based on the latest scientific advice from the British Geological Survey and the National Oceanography Centre, the likelihood of a tsunami affecting the area was assessed as once in 1,500 to 2,000 years.
"However, as severe winter storms can have an significant impact on coastal areas in Cornwall, the council has worked with partners to ensure that all areas prone to coastal flooding have produced flood plans. These are tested and checked annually and improvements made where required.
"The council is also involved with international testing with the Tsunami Programme as part of the Intergovernmental Oceanographic Commission of UNESCO and in 2014 took part in exercise NEAMWAVE14 which tested the European tsunami warning cascade system.
"A further exercise is due to take place next year when we will also be involved and will then use feedback from the exercise to refine our plans."