Brice was trying to impress his friends with his ability to slide down the parapet of the steps leading steeply from a railway bridge in the centre of Nantes. It is the kind of thing that seems like a good idea when you are 21; you are attending an open-air drinks party for 10,000 people; and you have drunk the equivalent of 12 glasses of whisky.

Brice, a student and volunteer fireman from a village in western France, fell 20 feet and smashed his skull and chest. He died later in hospital. The death of the young man - described by friends as gentle, charming and energetic - has shocked France. Young French people die in their dozens in road accidents each week after leaving bars or clubs. Brice's death was different. He is the first victim, a martyr to some, of a youth phenomenon sweeping France: the apero geant, or giant cocktail party.

The idea, driven by social networking sites, is to assemble as many strangers as possible to drink and chatter at spectacular town-centre sites in the open-air. The parties, which began in western France in March, have become an unofficial competition between French towns to gather as many young people as possible - a kind of Jeux sans Frontieres with wine, alcopops and hard spirits.

There was already growing public concern before Brice's death on Thursday night. Several apero geants have been banned, including one planned next to the Eiffel Tower in Paris for the week after next.

The events in Nantes have now launched an anguished national debate. Should the government step in? The interior minister, also a Brice, Brice Hortefeux, has convened a meeting of senior politicians and officials next week. Or would it be better, as one junior government minister suggested, to police the phenenomenon more closely and wait until the craze fades?

The idea of giant open-air drinks parties for young people, organised through the internet, is believed to have started in the US. It has taken off spectacularly in France since March for several reasons.

The French, even the young French, are very individualistic, but they like to do things individually en masse. It is also no coincidence that the aperos geants have been most successful in cities with large student populations: Renne, Nantes, Brest and - the record-holder with 12,000 people on Thursday night - Grenoble.

French universities do not have the same campus culture and crowded entertainment schedules as British universities. The idea of giant parties where young people could come together and have fun, and annoy their elders, filled a great vacuum.

The aperos geants are also a symptom, sociolgists say, of a shift in French society away from gentle, permanent tippling towards binge-drinking. The booze of choice at the gatherings is not beer or wine but tequila, vodka or whisky. Police said 72 young people were taken to hospital suffering from alcohol poisoning during Thursday's party in the centre of Nantes.

In other ways, however, the parties have remained very French. Until Thursday night - and that was a stupid accident - there have been few violent incidents. The parties are mostly agglomerations of alcoholic picnics in which groups of friends stay together and largely avoid talking to strangers.

A French sociologist, Monique Dagnaud, who studied the rave culture in France a few years ago, says the aperos geants are part of the same trend: the desire of young people for "collective apotheosis", or having a good time in big numbers. She also points out that the parties are an extension of the Facebook idea of collecting as many scarcely-known friends as possible.

The parties have been interpreted by other French commentators as the revolt of the internet generation against the notion that they are all bedroom-bound nerds incapable of social interaction except through a computer screen.

The minister for "youth and active solidarity", Marc-Philippe Daubresse, said yesterday that a blanket ban on Aperos Geants would be pointless and wrong. There should be more police surveillance to prevent further mishaps. "But there is no point in closing our eyes to the way that society is changing," he said. "You have to deal with causes not symptoms."

He said the giant parties reflected "the malaise of our young people, who feel the need to gather in tribes and party". The Socialist mayor of Nantes, Jean-Marc Ayrault called for all-party talks on the phenomenon. He also called on organisers to abandon the "stupid idea" of another giant party- a third - in the city next month.

The public prosecutor for Nantes, Xavier Ronsin, called for the competitive spiral between towns to end. "Where is the glory in this?" he asked. "What is so great about ... having 11,000 or 12,000 drunks in Nantes because Montpellier managed to assemble 10,000 drunks? Do you also want two deaths next time instead of one?"