"Prohibition is not effective", Jean-Marie Le Guen told France's BFMTV.
Other lawmakers - including fellow Socialists - dismissed the call, and a government spokesman said there were no plans for decriminalisation.
A recent WHO report found more French 15-year-olds smoked cannabis than in 41 other developed nations.
The study cautioned that "cannabis is a dangerous and harmful substance, especially for children and young people who use it regularly... Cannabis use is a risk factor for mental disorders and may trigger psychosis".
Mr Le Guen, who is secretary of state for relations with parliament as well as a medical doctor by training, said he opposed cannabis use and was a public health advocate who had always "fought against consumption of cannabis among the young".
But he said that approach had failed. Young people needed to be reached out to and taught that cannabis was dangerous, he said: "It is a health-based approach that I propose, not a moral or legal one."
Mr Le Guen cautioned that he was not speaking on behalf of government but suggested that the subject should be debated by the country's next president.
There have been repeated calls by leading government figures for the debate over cannabis to be reopened in France since President Francois Hollande came to power in 2012, but they have often been decried by fellow Socialists and opposition members and ignored by the administration.
That pattern appeared to be repeated on Tuesday, as Socialist Senator Samia Ghali told Europe1 that decriminalisation would only exacerbate drug trafficking.
"And what will we do tomorrow? Will we legalise cocaine and weapons because we cannot stem the flow of weapons? That's not serious!"
Laurent Wauquiez, of the centre-right Republican party, said "it seems like we are seeing the return of all the outdated ideas of the left. Do they really believe these are the questions being asked by French youths?"
Government spokesman Stephane Le Foll said the Socialist party was free to debate decriminalisation.
But he added firmly that the government was not re-evaluating the topic - "neither in work nor thought".
A French junior minister has sparked controversy by calling for renewed debate over the decriminalisation of cannabis.