STRASBOURG, France (Reuters) - Manuel Valls, the ex-French Prime Minister and leading candidate in the Socialist presidential primary, was flour-bombed by a protester in the northeastern city of Strasbourg on Thursday during a campaign walkabout at a Christmas market.

The man who aimed the flour at Valls, was protesting against a French parliamentary procedure known as “49.3” to force unpopular bills through parliament.

“We do not forget the 49.3. We don’t forgive it,” he screamed while aiming the flour on Valls as he entered a side-street cafe. The man was detained by the police.

Valls has said he would like to see the powers in the ‘49.3’ clause limited to budget legislation only. Changing it would require a constitutional reform which requires parliamentary votes and can involve a referendum.

However, Valls himself had used the so-called Article 49.3 of the constitution to force through a controversial labor reform this year while he was prime minister, upsetting fellow Socialists in the process.

“Very nice trip to #Strasbourg: a few grams of flour but pounds of smiles,” Valls tweeted on his official account, making light of the event.

“There is nothing worse than a campaign where nothing happens. We even got a little bombed with gluten-free flour,” Valls also quipped during a campaign stop later.