In the video, filmed in July 2016, the right-winger vowed to lead Italy out of the common currency if his party was to form a government.
Mr Salvini, 45, told an event in Rome that his party would quit the embattled eurozone without even holding a referendum on the issue.
He said: "You do not need a referendum because it would be a massacre for the Italian economy.
"I say that if the League goes to the government, we leave the euro."
He made the staggering comments just a month after Britain voted to quit the EU in the historic Brexit referendum.iPhone transfer software
The revelation will send further shockwaves through the EU, as Lega prepares to form a Eurosceptic coalition with the Five Star Movement.
The new right-wing government, which could be announced today, is set to challenge Brussels' fiscal rules and crack down on immigration.
Lega's attempts to join forces with M5S have repeatedly failed following March's general election, but a breakthrough appears to be in sight.