A huge Antarctic glacier could collapse within decades, causing a rapid rise in sea levels.

The Thwaites Glacier, the size of Britain, is ­losing 50 billion tons of ice a year, scientists say.

British and US scientists will investigate what is causing ice loss and how quickly the glacier could crash into the sea.

They fear the collapse of Thwaites Glacier and Pine Island Glacier could raise sea levels more than 3 ft.

It’s thought that without them the entire West Antarctic Ice Sheet could collapse, leading sea levels to rise 9 ft.

Professor Duncan Wingham, chief executive of NERC, said: “The fate of the Thwaites Glacier is one the big unknowns in Antarctic science. We currently do not know enough about the likelihood, timing and magnitude of the collapse of West Antarctic glaciers such as Thwaites for countries to be able to plan accordingly.”

“NERC and NSF, working together, are uniquely placed to attempt to reduce the scientific uncertainty about these unknowns, providing answers to one of the most important questions facing us about global sea-level rise.”

Glaciers contribute to sea-level rise when more ice is lost to the ocean that is replaced by snow.

The UK’s Science Minister, Sam Gyimah, said: “Rising sea levels are a globally important issue which cannot be tackled by one country alone.”

“The Thwaites Glacier already contributes to rising sea levels and understanding its likely collapse in the coming century is vitally important.”