The report by Jupiter Research, called Consumer Created Content, shows that while 53% of internet users are "passive, silent surfers", some 24% are now "unprompted contributors", ranging from those who have set up their own websites and weblogs to those who regularly make postings in forums.
The research found this active group are mostly young, male and spend long periods of time online. There is also a third group, identified by the report, of "prompted participants", who make up 23% of internet users, but restrict their interaction to taking part in polls and competitions.
Even though the more active bloggers and forum users are still in the minority, the report says that they "have a disproportionately wide influence and may seriously impact on brand communications".
It says that consumer brands can not afford to ignore the influence of bloggers and forums and urges marketers to ensure they are actively monitoring and engaging with them.
In an effort to catch the blogging craze, firms such as Honda and Nike have launched their own blogs, but these have come under fire.
Other firms including US retail giant Wal-Mart are now working directly with bloggers feeding them exclusives and suggesting topics for postings.
Julian Smith, Jupiter Research Analyst and lead author of the report, said: "Organisations ignoring community based influencers face the danger of small scale disgruntlement being exposed to a mass audience, resulting in a disproportionately large scale public relations problem that can directly affect their bottom line."
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .