A number of high profile firms have pulled their adverts from the social networking site Facebook after they were displayed alongside pages promoting the British National Party (BNP).
Vodafone and First Direct were the first to pull their ads after they appeared alongside groups in support of the BNP, which "exists to secure a future for the indigenous people" of Britain.
Virgin Media and AA followed suit, while other companies considered their relationship with the successful social networking site.
Advertisers cannot control where their adverts will appear on Facebook, which contains profiles for groups and people ranging from the BNP to Boris Johnson, Stephen Fry and thousands of regular users.
New Media Age editor Justin Pearse said: "On the internet you often have little control of where your ads are shown, something that's been highlighted by the unwitting association of some of the UK's favourite brands with a highly controversial political cause."
Vodafone said it did not support any political parties and had pulled the ads to "avoid misunderstandings".
A spokesman explained the company had purchased a "bundle" of advertising slots on a number of sites and was unaware it could appear next to a BNP group.
First Direct explained it was "obviously concerned about where our advertising appears".
"We have got to make sure that the places we advertise are consistent with our own values and identity," a spokesman for the bank said.
A BNP spokesman criticised the move and said "there's nothing wrong with the BNP".
"Unfortunately the media have created a bogeyman and really the fault lies with the media, who for some reason have vilified the BNP, and it has scared these people off."
Other companies with ads appearing alongside BNP groups declined to withdraw their adverts. Orange argued it would be a "knee-jerk reaction".