Six major firms have withdrawn advertisements from the networking website Facebook, after they appeared on a British National Party page.
Advertisers have no control over where on Facebook their ads appear
First Direct, Vodafone, Virgin Media, the AA, Halifax and the Prudential have all withdrawn ads. Virgin said it had to "protect its brand".
The advertisements appeared on a rotating basis on the BNP-related page.
A BNP spokesman said there was no reason to avoid the party. Facebook has declined to comment on the decision.
Mobile phone giant Vodafone and bank First Direct were alerted to the positioning of the ads by New Media Age magazine, while Virgin Media, the AA, Halifax and the Prudential withdrew later.
The spokesman for the BNP said: "There's nothing wrong with the BNP."
He added: "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."
However, the firms expressed concern over the ads' positioning.
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."
First Direct spokesman Rob Skinner said: "We are 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."
Vodafone said it wanted to continue to work with Facebook while "staying true" to its policies.
A spokeswoman for the mobile phone giant said it bought bundles of advertising space across a number of websites.
"As a result we were not aware that a Vodafone advertisement would appear next to a British National Party group on Facebook," she said
"Our public policy principles state that we do not make political donations or support particular party political interests and therefore to avoid misunderstandings we immediately withdrew our advertising as soon as this was brought to our attention."
The Prudential also said its policy was not to advertise with any political party.
A Virgin Media spokeswoman said: "We want to advertise on social networks but we have to protect our brand".
She said the company was now talking to its advertising agency to find ways of giving it some control over where its adverts would be placed online.
The AA also said it booked advertising space through a specialist agency and had "strict procedures in place with its agency to ensure it does not advertise on inappropriate sites."
It said it had recently pulled ads from YouTube after the BBC Panorama programme showed that videos of children fighting were being regularly uploaded.
In a statement, the Halifax said the position of ads on the site "is such that it may appear that we support the owners of specific pages. This is not the case."