Britain First may have been thrust into the centre of global politics by Donald Trump, but those familiar with the inner workings of the far-right political group portray a factionalised rabble, riven by jealously and petty infighting.

People who have mixed with the group’s senior echelons also describe mammoth drinking sessions, threats of violence and boasts of inciting conflict with Britain’s Muslim community. Speaking publicly for the first time, Graham Morris, a former boyfriend of Britain First’s deputy leader, Jayda Fransen – whose anti-Muslim videos were retweeted by Trump last week – said he had left the group because it “was out of control” and some members advocated violence.

Morris revealed tensions between the group’s leader, Paul Golding, 35, whom he described as a “narcissist” and who was extremely jealous of his relationship with Fransen, 31. Morris, 54, who lives near Hinckley, Leicestershire, and left Britain First several months ago, also revealed how members would plot large-scale anti-Muslim attacks, describing one such plan hatched after a Britain First demonstration in Birmingham in June.

“They were talking about damaging mosques up and down the country, targeting them at the same time. I’ve got a young child, I didn’t want to be part of any mosque attacks, that sort of thing,” he said.

He also described how the group’s security guards would be told to “kick people’s doors in”, and that despite the group claiming officially to reject “racial hatred in all forms” some members were openly racist.

Experts who have followed the rise of Britain First insist that President Trump’s extraordinary intervention will ultimately fail to have an electoral impact. Despite having 1.9m Facebook likes and 27,000 Twitter followers, the group is believed to have attracted fewer than 1,000 members.

Matthew Collins, of the anti-fascist group Hope Not Hate, said: “It has internal difficulties and ongoing legal cases that have very little to do with politics and more to do with the culture of the party, which is one of jealousy, drinking and intimidation. There’ll be no political gain and they won’t be standing in more elections, they’ll just intimidate more people and beg for more money.”

Collins said that, despite last week’s massive publicity, the party was unlikely to avert what he called a gradual decline.

“The nature of Britain First is that during the last six to 12 months it has become more and more extreme, returning to its British National party roots and the relationship between its senior members is unlikely to be repaired.”

Morris, who said he became involved with Britain First earlier this year because of his concerns over sharia law, said he quickly became disillusioned with its racist and violent tendencies. On Friday Fransen threatened New York Times reporters who sought to interview her with “home visits of their own”.

Morris’s misgivings first began during the Britain First protest in Birmingham in June when Fransen invited his 10-year-old son on to the stage.

“She was asking me to bring my son to the demonstration and then she took him on stage, then there was a picture of my son on stage, used in a publicity stunt, like some sort of poster boy. I wasn’t very happy with that and we started falling out,” added Morris, who said that he had contacted the police regarding harassment since he had left the group.