Justin Bieber -- 'I Would Never Trash Argentina's Flag!'

Justin Bieber could face prison time if officials in Argentina decide to nail him for treating the country's flag like a dirty rag at a recent concert ... but Bieber's camp tells TMZ it was never his intention to desecrate the national symbol.

During a concert in Buenos Aires on Saturday ... Bieber appeared to use his mic stand to mop the floor with a flag that had been thrown onstage by a fan ... and video of the incident continues to fuel Argentinian anger.

A rep for Justin tells TMZ ... Bieber would never, ever desecrate a flag -- and the whole thing is a giant misunderstanding. We're told that female fans were throwing bras and t-shirts on stage -- which is pretty typical -- and Justin was merely trying to brush them off the stage so he wouldn't step on them.

As for the flag ... we're told it wasn't a flag at all ... but rather a T-shirt with the Argentine flag printed on it and Justin didn't realize the item sported the national symbol.

We spoke to diplomatic officials at embassies in Buenos Aires and in Washington ... they tell us people are PISSED by what they perceive as Justin's disrespect for Argentina. One lawyer in Cordoba has reportedly filed legal papers denouncing Bieber for "insulting the flag."

Still ... it's highly unlikely Justin will be going to jail for his actions ... there's no indication authorities will charge him -- even though desecrating the flag IS a crime in Argentina punishable by 1 to 4 years in prison.