"Yellow vest" protesters are more likely to believe conspiracy theories than other French people, according to a survey published Monday.
Nearly a quarter believe a gun attack on the Christmas market in Strasbourg in December was ordered by the French government to deflect attention from the anti-government protests, an Ifop poll for Conspiracy Watch and the centre-left Jean Jaures Foundation found.
And a further fifth continues to have doubts about the official account of the attack in which five people died, it said.
"Yellow vest" activists are also much more likely to give credence to shadowy "Zionist plots" and a popular conspiracy theory that mass immigration is being organised by the elites, it found.
In general, one in 10 French people thought the Strasbourg attack was part of a government plot to "distract attention and create fear" when the protests were at their height, Ifop said.
People who passively support the movement, however, were much less likely to question the official line that radicalised small-time criminal Cherif Chekatt was responsible for the killings, the survey said.
The "yellow vest" movement, now in its 14th week, began as a revolt against a rise in fuel prices but has since morphed into an expression of general discontent.
Its leaders and supporters have been blamed for a tsunami of fake news on social media, with journalists the target of numerous attacks and threats at gatherings and demonstrations.
The amorphous movement -- which has no leadership structure -- has become one of the most long-running revolts in recent French history and tends to be strongest in the countryside and provincial towns.
Driven by social media
Its populist platform includes a long list of competing demands from lower taxes and increased public services to direct democracy through regular referenda.
The survey found that nearly half of "yellow vest" protesters believe in a worldwide "Zionist plot" as well as the far-right "Great Replacement" conspiracy theory, which posits that elites are organising "immigration deliberately to replace Europe's native populations".
Ifop said a clear majority were also convinced that the French "health ministry was working for hand in glove with the pharmaceutical industry to cover up the danger of vaccines".
A quarter of the general population subscribe to similar beliefs, it found, sparked by the 1998 MMR vaccine-autism scare, which has been described as "perhaps the most damaging medical hoax of the last 100 years".
The survey was carried out through an online questionnaire on a representative group of 1,506 people in the week leading up to Christmas, with a second later sample of 254 people.
At the time, half of the people surveyed said they backed the yellow vest movement.
Ifop said it asked participants if they had taken part in yellow vests protest or if they merely supported the movement, and was then able to hone in on each groups' opinions.
Protesters were "extremely dependent" on social media and YouTube for their news, where conspiracy theories flourish, the survey also found.
Nearly 59 per cent go first to Facebook newsfeeds for the headlines, it said, compared to 37 per cent of the general population which tends to get its news from traditional media.
The 'yellow vest' movement, now in its 14th week, began as a revolt against a rise in fuel prices but has since morphed into an expression of general discontent.