The reporter was asking about teargas that had been used earlier in the day on steelworkers who had tried to storm the president's Paris campaign headquarters.
The angry steelworkers from an ArcelorMittal plant in Florange are worried about job losses. The fate of the plant has become a hot topic in the presidential campaign.
Asking about the television footage of steelworkers being confronted by riot police and fired against with tear gas, the reporter said "you'd rather have avoided that, wouldn't you?"
"Why should I give a damn about what you're saying?" replied Sarkozy to the journalist, who works for 24-hour news channel LCI.
"What do you want me to say to you?"
"I don't know," replied the reporter, who looked somewhat surprised at the remarks.
"What a dickhead," said the president as he walked off while one of his aides said to the reporter "your time has come."
Sarkozy then thought better of his remark and turned, touching the reporter on the shoulder and saying "he's a nice guy, he's young."