The rise of video-sharing websites such as YouTube and Dailymotion is proving to be a headache for some of France's biggest companies as their image comes under fire from satirical online videos.

The aim behind humorous video clips can vary -- some are made by film producers as publicity stunts, others simply for fun -- but the potentially global impact and unpredictable nature of the clips can make them difficult for companies to contain.

Brands were in the mindset of having one message, one broadcast, Emmanuel Vivier, chief executive of marketing agency Vanksen, said. Now people reply to the brands' messages, remix them, redistribute them... impacting their reputation.

It's becoming harder and harder to tell the difference between a real advert and a fake one, he said.

French grocer Carrefour, the second-biggest retailer in the world, was last month forced to disown and condemn a fake video advert that implied its discount food range contained human remains.

The video, which first appeared on Google site YouTube in early December, depicts an angelic little girl munching reluctantly on her grandmother's bones as her parents egg her on.

It was a concern for us, a Carrefour spokeswoman said. It did not give a good image for the brand.

Phone network operator France Telecom also squirmed under the online spotlight after a succession of employee suicides last summer prompted multiple video parodies.

One clip posted on Dailymotion in October shows several France Telecom workers killing themselves in a variety of ways to the tune of Don't Worry, Be Happy. It features the slogan Souffrance Telecom -- or Suffering Telecom.

There are a lot of things that go on the web that we're obviously not comfortable with, said a France Telecom spokesman. But, he said, it was generally not very productive to respond directly unless the law was being broken.

Another regular target has been French bank Societe Generale , which provided rich comic fodder online during the financial crisis of 2008 and 2009. Its coup de pouce -- or helping hand -- ad campaign featuring a giant thumb helping out was remade several times to poke fun at the bank.

GROWING PRESSURE

Some blue-chips have used online video and multi-media marketing campaigns to their advantage, such as ArcelorMittal, with its online TV channel, and Danone, whose multi-media ad for Evian features babies on roller skates.

But most leading companies in France are still playing catch-up and only responding to negative items rather than using online video to create their own content, marketing experts said.

The pressure will likely increase as mobile phones such as the Apple iPhone 3GS and social networks like Twitter put more online video on the Internet.

The problem for big companies is partly one of stretched resources and also of old-fashioned approaches to marketing, said Andrew Girdwood, head of strategy at British consultancy BigMouthMedia.

The bigger you are, the harder it gets, Girdwood said.

Conversely, smaller companies were better placed to create content and gain publicity via video-sharing sites, according to Girdwood, as they were less likely to have a legacy marketing strategy and would profit more from online exposure.

Blogs could also help companies by creating an open and transparent discussion forum to ease consumer frustrations and create a personal connection, said Vivier, of marketing agency Vanksen.

If you don't capture the (online) territory, you leave it entirely open to others, he said, adding that companies were more likely to suffer from criticism if they failed to build an online presence.

It's like karma, he said.

(Editing by Sharon Lindores)