Around 300 million people will be vulnerable to annual flooding by 2050, three times as many as previously thought, according to a new climate change study.

Researchers concluded that previous ground elevation data vastly underestimated the extent to which coastal zones will be subject to flooding during high tide or major storms.

Data gathered by Nasa from a space shuttle mission has been widely used in previous predictions.

But the latest study used more accurate information from laser-based systems on aircraft.

Ben Strauss, chief scientist of Climate Central, a US-based research group, said: "Sea-level projections have not changed. But when we use our new elevation data, we find far more people living in vulnerable areas than we previously understood."

Part of the problem with the Nasa system was that it mistook rooftops and trees for ground level, he said.

Mr Strauss added: "It turns out that for most of the global coast we didn't know the height of the ground beneath our feet."