The UK's advertising regulator will be vetting websites including Twitter and Facebook from today after receiving thousands of complaints about online marketing.
For the first time the Advertising Standards Authority is to police companies' online marketing, including social networking sites.
Since 2008, the ASA said it has received more than 4,500 complaints about online marketing which did not fall under its remit until now. The move is in response to a recommendation by the UK advertising industry.
Previously, the ASA's remit extended only to traditional TV marketing and paid-for adverts online. It will now be able to censure marketing through non paid-for sites, such as Twitter and Facebook, which are becoming increasingly popular promotional tools.
The watchdog has increased its complaints and investigation staff by 10% to about 70 people since January, to deal with the anticipated increase in complaints about online marketing that now fall under its remit.
Lord Smith, chairman of the ASA, said: "This significant extension of the ASA's remit has the protection of children and consumers at its heart."
Andrew Brown, chairman of the Committee of Advertising Practice, which draws up ASA regulation, added: "Extending the online remit of the ASA has been a top priority for UK industry over the last couple of years.
"Our aim has been to extend further in the online world the principles that are already well established in our system, namely those of effective consumer protection and fair competition."
The ASA said it will not censure members of the public for sharing material which has already been banned.
Many TV ads, including Beyonce's banned campaign for the perfume company Coty UK, quickly appear on YouTube and other video sharing sites after being uploaded by members of the public.
The ASA can order censured companies to immediately withdraw online marketing and will now "name and shame" businesses that do not comply with its extended remit.
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