FRANCE (REUTERS) - French presidential hopeful Manuel Valls was slapped while out on the campaign trail on Tuesday (Jan 17), as the former prime minister struggled to defend the government's record ahead of a primary to pick the Socialists' candidate for the presidency.

A young man lightly hit Valls as he visited the small town of Lamballe in Brittany, before being wrestled to the ground by a security guard and subsequently arrested. As of Wednesday morning he was still in police custody.

Asked about the incident during a radio phone-in on Wednesday morning, Valls said he would not let the incident distress him but one caller suggested the youth's anger was reflected elsewhere in the country.

"I just wanted to say, Manu, I don't know whether or not you think it's OK but I think there are 66 million of us who want to give you a slap. It was just amazing, I'm not kidding. He was perfect that guy, just great," said the caller calling himself Guillame from Grenoble.

Valls said he would lodge a formal complaint against the man, whose motives were not yet known. If prosecuted he could face up to three years in prison and a 45,000 euro (S$68,347) fine.

Valls defended his decision.

"A society needs rules, needs taboos. We're in a democracy: debates, questions, protests, are obviously essential for a democracy. It's a pleasure to go and meet the French people, I love it, I've always done it because it allows you to be in touch with people, to talk to them, to be questioned by them, to be shouted at by them, and thank goodness because that's democracy, but violence? Wanting to hurt someone? That's unacceptable," he said.

Polls show that the primary will be a tight race between Valls and leftist former ministers Benoit Hamon and Arnaud Montebourg.

All but two of the candidates will be eliminated before a second round on Jan 29 but polls show whoever emerges victorious is unlikely to win the presidential election in the spring.