Almost half of French people believe it is acceptable for workers facing layoffs to lock up their bosses, according to an opinion poll published on Tuesday.

Staff at French plants run by Sony, 3M and Caterpillar have held managers inside the factories overnight, in three separate incidents, to demand better layoff terms -- a new form of labor action dubbed "bossnapping" by the media.

A poll by the CSA institute for Le Parisien newspaper found 50 percent of French people surveyed disapproved of such acts, but 45 percent thought they were acceptable.

"They are not in the majority ... but 45 percent is an enormous percentage and it demonstrates the extent of exasperation among the public at this time of economic crisis," Le Parisien said.

On March 31, billionaire Francois-Henri Pinault was trapped in a taxi in Paris for an hour by staff from his PPR luxury and retail group who were angry about layoffs. Riot police intervened to free him.

Le Parisien found that 56 percent of blue-collar workers polled approved of bossnappings while 41 percent disapproved. Among white-collar workers, 59 percent were against the practice while 40 percent thought it was acceptable.

"These hostage takings, we know how it starts but no one knows how far it can go," said Xavier Bertrand, a former labor minister now secretary-general of the ruling UMP party.

"Our country must avoid entering a spiral of violence," he said in reaction to the opinion poll, adding that bossnappings "cannot be tolerated."