The social network said it was "very cautious" about removing political speech.
The details emerged as the Home Affairs Committee grilled Facebook, Google and Twitter on what they were doing to combat hate speech.
MPs said the firms had made progress but were still not doing enough.
Google promised an annual transparency report on the issue. Facebook and Twitter said they were looking at a similar course of action but did not commit to it.
On Britain First, a far-right group, Facebook's director of public policy Simon Milner said it was reviewing its future.