LONDON (Reuters) - The British government has halted its advertising on the social networking Web site Facebook over concerns about how its ads are displayed, its communication arm said in a statement.

Six major British companies, including cell phone giant Vodafone , pulled their ads from Facebook last week because they were appearing on the profile page of the far-right British National Party.

Ads pop up on Facebook pages on a rotating basis, giving companies limited say over where they are displayed.

The Central Office of Information (COI) said it was seeking assurances that ads on social networking Web sites would reach desired audiences. It said it would not resume advertising until better safeguards were in place.

COI, which has one of the biggest advertising budgets in Britain, said on Tuesday it was still waiting for guarantees from Facebook but that it was satisfied with the safeguards in place on the rival MySpace and Bebo Web sites.

"Advertising has been paused temporarily on any Web sites that have not provided COI and i-level (COI's online media-buying agency) with the further assurances our bookings require," Jamie Galloway, COI director of digital media said late on Monday.

Facebook, which has seen membership spike to more than 30 million and is rapidly becoming one of the most popular sites on the Internet, was not immediately available for comment.
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