The deputy leader of far-right group Britain First has been found guilty of religiously aggravated harassment after hurling abuse at a Muslim woman wearing a hijab in front of her four young children.

Jayda Fransen, 30, was fined nearly £2,000 at Luton and South Bedfordshire magistrates court for wearing a political uniform and shouting at Sumayyah Sharpe during a “Christian patrol” of Bury Park in Luton on Saturday 23 January.

Fransen admitted telling Sharpe that Muslim men forced women to cover up to avoid being raped “because they cannot control their sexual urges”, adding “that’s why they are coming into my country raping women across the continent”.

But she denied the words were intended to be offensive.

“The reason I said them was because from everything I have studied, I understand them to be true,” Fransen said in her defence.

District judge Carolyn Mellanby said she believed the group had gone to the area looking for trouble – but said Sharpe had been mistaken for an easy target.

“I have no doubt the words used towards her [Sharpe], in her expression, represented everything against her and what she believes in,” she said. “In other words, offensive, insulting, abusive and, in my judgment, intended to cause offence and alarm and distress to her religion.”

About 20 Britain First members took part in the “patrol” of Bury Park, distributing branded newspapers which had a front page that said: “World War Three has begun – Islam against the world,” the court heard.

Sharpe, who was shopping with her four young children at the time, refused a newspaper from the group.

Giving evidence on Wednesday, she said it was at this point that Fransen, from South Norwood, south London, crossed the road and confronted her. The incident was captured on camera by members of Britain First.

Sharpe told the court: “She came across, shouting at me, saying, ‘Why are you covered?’ and she said that quite a few times. I told her it was my choice that I cover.

“I then turned to the camera and I said, ‘Film me, I’m British, I’m a British Muslim. It’s my choice to wear this clothing and it’s my right.’”

She added: “I called her a slapper, I admit, and I told her to piss off because I was so angry at that point that she had done that in front of my children.”

In video footage shown to the court, Fransen was seen brandishing a white cross as she told Sharpe that Muslim men made women cover themselves so that they were not raped.

Following the incident, Sharpe said she had to go home and explain the meaning of the word rape to her young children.

She also told the court her four-year-old son was now scared to leave the house in case they ran into the group.

Mellanby described Fransen’s behaviour as “shocking” and commended Sharpe for the “eloquent” account of events she had provided to the court.

Footage of the incident with Sharpe was edited and included in a video posted on the party’s YouTube channel.

The judge said she was aware that as a result, Sharpe had been branded a terrorist on some websites.

Fransen, who was elected deputy leader of Britain First in autumn 2014, was also found guilty of wearing a political uniform in a public place. She was dressed in a green coat with a Britain First lapel and black beanie hat bearing the party’s emblem during the patrol, which Mellanby ruled was similar attire to the rest of the group and signified her association with the party.

Fransen was fined £1,000 for the religiously aggravated harassment and £200 for wearing a political uniform.

She was also ordered to pay £620 in costs – as well as a £100 surcharge – and issued with a two-year restraining order to prevent her from contacting Sharpe or engaging in intimidating behaviour towards her.

A further charge of failure to surrender to police bail was withdrawn by the prosecution.

Following the hearing, a Britain First supporter was arrested on suspicion of common assault after an alleged altercation with a journalist.

Fransen, who is described by Britain First as a “devout Christian”, condemned the court’s verdict in a video posted to the group’s Facebook page.

She said: “It was just absolutely absurd in the court. It was just a really clear display of Islamic appeasement. That’s all that we’ve just seen.”