Britain First is a far-right, British fascist and neo-fascist political party and hate group formed in 2011 by former members of the British National Party (BNP). The group was founded by Jim Dowson, an anti-abortion and far-right campaigner. The organisation's co-leaders are former BNP councillor Paul Golding and Ashlea Simon. Jayda Fransen formerly served as its deputy leader.

Britain First campaigns primarily against multiculturalism and what it sees as the Islamisation of the United Kingdom, and advocates the preservation of traditional British culture. It attracted attention by taking direct action such as "Christian patrols" and "invasions" of British mosques. It has been noted for its online activism.
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Despite the initial unwillingness to regulate Britain First and similar movements, public pressure continued to mount. In December 2017, Twitter suspended the accounts of Britain First and its leaders Golding and Fransen, after revising its rules on hate speech. When asked, Twitter declined to comment, citing privacy and security reasons. In March 2018, Britain First was banned from Facebook, which said it broke community guidelines and was designed to incite racial hatred. In its official statement on the matter, Facebook stated that this was due to "repeatedly posted content designed to incite animosity and hatred against minority groups". This was received very positively among many across the political spectrum. In a statement, the Mayor of London, Sadiq Khan said, "Britain First is a vile and hate-fuelled group whose sole purpose is to sow division. Their sick intentions to incite hatred within our society via social media are reprehensible, and Facebook’s decision to remove their content is welcome."
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On 16 June 2016, Jo Cox MP was fatally shot and stabbed outside a library in Birstall, by a man who eyewitnesses said shouted "Britain first" as he carried out the attack. One witness told BBC News that he was uncertain whether the suspect was shouting "Britain first" or "put Britain first". Another man said that he did not hear the words at all. The party issued a statement denying any involvement or encouragement in the attack and suggested that the phrase "could have been a slogan rather than a reference to our party". The group's leader, Paul Golding, condemned the attack, saying, "We hope that this person who carried it out is strung up by the neck on the nearest lamp post. That's the way we view justice."

Following this, the far-right organisation National Action (which lauded Cox's murderer) became the first far-right group to be proscribed as a terrorist organisation in December 2016. In November, several months after Cox's murder, the Labour MP Louise Haigh said that the House of Commons should open a debate on the issue of Britain First's proscription, saying to The Independent that "the threat and violence of the extremist political right is of serious concern", adding that "we need a full and frank debate in this country about how such hate-filled, violent extreme right organisations are threatening and undermining the values we hold dear". Following this debate, Haigh received a number of death threats, saying that on one day "an individual went through every one of my YouTube videos and said he would not rest until I was murdered. If that is not evidence that Britain First should be proscribed as a terrorist organisation, I am not sure what is".

https://en.wikipedia.org/wiki/Britain_First