Gibraltar Chief Minister Fabian Picardo made the comments to visiting delegates from the UK Foreign Affairs Committee of the House of Commons on Wednesday.
"If we had to apply our minds to an economic model that might enable us to survive UK exit from the European Union, it might be possible to design something where a lot of belt tightening might mean that we might not actually disappear economically from the map," said Picardo after the meeting.
"The snapshot is that it would be a disaster," he was quoted as saying in the Gibraltar Chronicle.
The chief minister also stressed it was key that Gibraltar was included in any legislation concerning a possible UK referendum on an exit from the EU, but admitted votes from the territory wouldn't carry much weight.
During the meeting, The Rock's top politician also took aim at London for not paying enough attention to the concerns of the tiny UK-held territory, according to the UK's Telegraph newspaper.
Tensions between London and Madrid have been high since mid-2013 when Gibraltar placed a number of blocks in coastal waters to create an artificial reef, causing conflict with Spanish fisherman.
Spain fought back by stepping up border controls, slowing traffic at its border with Gibraltar.
But while Picardo on Wednesday lauded the UK's "very robust" attempts to address this problem, he said not enough had "happened to deter Spain’s activity".
"Spain cannot get away with thinking that she can punish and damage Gibraltar at her whim and still say that the relationship with the United Kingdom is excellent," the Telegraph had Picardo saying.
Britain has held Gibraltar since 1713 but Spain wants it returned and refuses to recognize British sovereignty over the waters off the land known as "the Rock".