Brexit campaign group Leave.EU's Facebook videos have become some of the first to be removed by the social network as part of a crackdown on political "dark ads".
Leave.EU failed to provide details now required by political advertisers.
"Their delivery was 'not approved', presumably because they didn't have a disclaimer as of today," Leave.EU spokesperson Andy Wigmore told Sky News. "All ads are now inactive."
Under Facebook's new regulations, which went into force on Thursday, advertisers running political ads must provide certain details, or have their ads taken down.
Advertisers must confirm their identity and location to Facebook, and say who paid for the ad, before they can be approved to run political ads.
Advertisers must also prove to Facebook that they are paid for by someone who lives in the UK.
Ads that have gone through this process come with a "paid for" disclaimer showing who has paid for them. They are also filed in Facebook's library of political ads.
At 5pm, Leave.EU had two "suggested page" ads running, promoting its pages to non-fans.
However, at 6pm, Leave.EU received an email from Facebook which said: "We have reviewed some of your ads more closely and have determined they don't comply with our advertising policies."
At that point the ads were made inactive, which meant they didn't appear on Leave.EU's Facebook page.
That, Mr Wigmore said, was the first he knew about the policy.
"We've never received anything directly from Facebook about this and [are] currently trying to find out how we register ourselves with them as a political campaign," he said over email.
"We think it's a good thing that these notices are put on all ads so people know who they have come from – we fully support the new Facebook policy."
So-called "dark ads" target voters based on the tiniest details of their lives, using age, location, gender and interests to cater precisely to each person's predilections.
Until Thursday, there has been no requirement to declare political spending on Facebook, so groups have been able to field political ads without making it clear what they were or who they came from.
Leave.EU, which was founded by businessman Arron Banks, played what its website describes as "a decisive role" in the EU referendum.
Banks, who provided £8m in funding to the Leave.EU campaign, is currently being investigated by the National Crime Agency over allegations that he was "not the true source" of the money.
Since it was first announced in October, Facebook's ad transparency drive has been marred by a series of embarrassing mistakes.
The firm's system allowed one set of adverts to be falsely labelled as "paid for by Cambridge Analytica", and another as "paid for by the Islamic State". In order to fix the errors, Facebook delayed the launch by two weeks.
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Facebook's Rob Leathern said the firm had added "more controls to help prevent politically motivated actors looking to use false news or sensationalism as weapons" into the new system.
He added: "This helps shine a brighter light on political advertising and offers a resource for news organisations, regulators, watchdog groups and the public to hold advertisers more accountable."
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Sky News
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