Police are investigating a group of far-right members of the UK’s embryonic “yellow-vest” movement who accosted the Conservative MP Anna Soubry outside parliament and called her a traitor, the Observer can reveal.

Senior Met officers have studied the group’s own video, which shows them harassing the pro-Remain MP, and believe a public order offence may have been committed.

Commons Speaker John Bercow contacted Soubry asking how he could help after the incident on Wednesday, during which far-right supporters shouted the MP was “on the side of Adolf Hitler”.

Soubry said: “A senior officer in parliament then contacted me and he downloaded and watched the entire video and he took the view that a public order offence had been committed and they are now investigating.”

The group’s leader, James Goddard – whose use of the word “traitor” is the same term used by members of the far right to describe the murdered Labour MP Jo Cox – filmed himself calling Soubry a “disgrace to the country” because of her tenacious campaigning for a people’s vote.

In a Live Facebook broadcast on Friday afternoon, Goddard – who declined to talk to the Observer – defended the targeting of Soubry, saying that “we attacked her with a bit of verbal”.

Goddard, who styles himself as a Brexiter, has posted anti-Muslim messages on the social media site Gab, including messages stating: “Wherever Islam exists you will find murder and rape” while another calls for mass deportations of “illegals”. He also gave a speech at a rally in the summer supporting the far-right activist Tommy Robinson, whose real name is Stephen Yaxley-Lennon.

Soubry said that the group should not be considered pro-Brexit supporters but viewed as extremists.

Far-right activist James Goddard outside parliament. Photograph: Paul Davey/SWNS

The development comes as the Observer has learned that BNP founder Nick Griffin is among a cohort of prominent far-right figures keen to hijack the UK’s yellow-vest movement, which has recently appropriated the high-visibility jackets worn in the French gilet jaune protests.

Griffin has established links with a recently formed group called Liberty Defenders that purports to fight for civil rights. This group is attempting to establish itself as a prominent part of the UK’s yellow vests and in turn hoping to hijack the Brexit debate to gain support.

According to Hope Not Hate, which monitors far-right activity, prominent members of the group include former soldier Tim Scott, who once led the UK branch of Germany’s anti-Islam group Pegida, and former Ukip candidate Jack Sen, who was suspended from the party over racially charged comments.

After the Soubry incident Griffin, who was ejected from Hungary last year on the advice of the country’s counter-terrorism police, tweeted that: “the Yellow Vest Movement is here to stay & will only grow.”

The former far-right leader also sent a link to an online Liberty Defenders piece requesting an interview with him and Sen to be retweeted to “help build the resistance!” Below the interview on the Liberty Defenders website, Goddard is described as one of Britain’s “most honourable activists” and is praised for his part in the yellow-vest protests in central London, which hoped to “demand our government give us the Brexit we voted for”.

Matthew Collins of Hope Not Hate said: “Hiding in the recesses of all this is Nick Griffin. He’s got more spare time on his hands than ever before and he’s desperately trying to resurrect himself with Brexit.” The group said messages sent by Goddard showed he was “a vile racist yob, pure and simple.”

Other yellow-vest protesters thought to be involved in the incident involving Soubry include David Coppin of Margate, an EDL supporter who has attended numerous far-right rallies across the UK including a “White Lives Matter” march.

Live Facebook broadcasts last week showed the small group shouting verbal abuse through a megaphone at pro-Remain protesters and journalists broadcasting from outside parliament, with Sky’s Kay Burley made a particular target.

On Thursday a group called “The Official UK Branch of the Yellow Vests” went up on Facebook, along with a “code of ethics”, which said: “We seek only to inform and encourage the reinstallation of British interest [sic] in parliament.”