The Government is expecting a 100 per cent “yes” vote when the islanders are asked on March 11: “Do you wish the Falkland Islands to retain their current political status as an Overseas Territory of the United Kingdom?”

Intelligence chiefs have warned David Cameron that a resounding “yes” vote could lead to an aggressive “stunt” by the Argentine government, such as the planting of the country’s flag on the island by a small raiding party.

Other possibilities include a “cod war” style harassment campaign by the Argentine navy of the Falklands’ fishing fleet and the disruption of British oil and gas exploration.

Such a move, officers have warned, could quite quickly escalate into aggressive action if the Royal Navy was ordered to intervene.