The young centrist burst into laughter when he recognised the drug’s pungent smell, before jokingly warning youngsters that smoking wouldn’t help them with their schoolwork.
Mrs Le Pen, leader of Front National, told the French news channel BFM TV: “Mr Macron enjoys visiting drug-infested neighbourhoods and joking about marijuana use.
“It makes him laugh, apparently. But let me tell you this – his jokes do not make Guianese people laugh.
“Drug trafficking is a huge problem in French Guiana, and Mr Macron thinks it’s okay to joke about it. He finds it funny to see people smoking marijuana in one of the capital’s most dangerous neighbourhoods.”
She said it shows “how little he knows” about France’s overseas territories.
The 39-year-old head of state was posing for pictures with locals in the capital Cayenne’s impoverished La Crique neighbourhood on Friday night when he caught a whiff of marijuana, and cracked a joke about how he was still able to recognise the drug’s distinctive smell.
He said to a chorus of laughter: “Well, well, some of you aren’t just smoking cigarettes, huh?”
“I still recognise the smell! But this, this won’t help you do well at school… Make sure you tell other youths that,” he can be heard telling the smokers on a video posted to the Elysée palace’s official Facebook page.
Mr Macron’s rocky three-day visit to the French territory in South America was marred by violent protests over the lack of government aid.
At 23 per cent, the unemployment rate in French Guiana is more than twice that of mainland France, and many Guianese feel as if they are overlooked by the government in Paris.
Demonstrations in March and April this year triggered a series of nationwide strikes and led to promises of two separate aid packages worth billions of euros, although tensions have eased little since then.
Mr Macron, who said during his trip that he was “not Father Christmas,” did however pledge to end the “asymmetric relationship” between Paris and Cayenne, adding that his trip “marked the beginning of a new chapter”.