Leaflets claiming to be from the British National Party (BNP) have been posted to West Yorkshire residents accusing murdered MP Jo Cox of having taken "misguided action" by "helping Muslims", the Commons has heard.

Labour MP Paula Sherriff said people living in her constituency of Dewsbury had received literature from BNP activists making a number of "horrendous allegations".

Cox, 41, MP for Batley and Spen, was shot and stabbed to death after a constituency meeting in Birstall on 16 June. "Many members will be aware that my constituency sits right next door to Batley and Spen," Sherriff MP told the Commons on Wednesday (29 June).

"Yesterday, people in my constituency received a leaflet from the BNP saying Jo Cox took misguided action by helping Muslims in the country who may now go on to join Isis (Islamic State), alongside some other horrendous allegations.

"Then I have received a significant number of communications from constituents, one – a seven-year-old Muslim girl – was told on Friday, I've removed the expletives from this for the purpose of this House, 'it was the best day ever today, go home all of you' to her and her family. And I am continuing to receive a number of similar incidents."

Home Office minister Karen Bradley said she was "shocked" by the reports, describing them as "utterly unacceptable". She added: "I would like to meet you if you would allow and perhaps we can discuss a specific action being taken and make sure that any crimes such as those are reported and actions taken against them."

The BNP, an anti-immigration party formerly led by Nick Griffin, strongly denied it was responsible for the leaflets and suggested they had been fake.

David Furness, a BNP spokesman and former London Mayoral candidate, told IBTimes UK: "I've spoken to our head office and these are not official BNP leaflets. We would never do such a thing and we have not recently sent out material to that area. They sound like fake leaflets – something that's happened to us before – and somebody is trying to slur the party."

Furness said he wanted the police to investigate and examine any posted material claiming to be from the BNP for "DNA or fingerprint evidence".

Conservatives, Liberal Democrats and Ukip have all said they will not contest the upcoming by-election for Cox's now vacant seat. Furness said the BNP would also not field a candidate. However former BNP member Jack Buckby announced his intention to contest the seat as a representative for anti-Islam party Liberty GB.

Buckby said he found Cox's death "tragic" but accused the Labour Party of being "responsible for the demographic and cultural assault on Britain which has already done great damage in areas of Yorkshire".