Jewish leaders have joined Christian, Muslim, Hindu, Sikh and Zoroastrian communities in calling for the British government to stop “psychopathic” Islamic extremists in Iraq from “systematically slaughtering” religious minorities.

Dayan Ivan Binstock, a leading member of the Beth Din, and Senior Reform Rabbi Laura Janner-Klausner signed up to a rare show of unity, as the six faith groups warned of the “extermination” of Christians and other religious minorities in Iraq.

An image taken from a propaganda video shows ISIL militants in Iraq's Nineveh province

An image taken from a propaganda video shows ISIL militants in Iraq’s Nineveh province

They called on David Cameron to use the UK’s influence to start bringing war crimes prosecutions against rampaging militants from Islamic State (IS), the group responsible for beheading an American journalist this week.

Forced conversions, beheadings and crucifixions of Christians, Yazidis and others amounted to a “tragedy of historic proportions”, they said in an open letter.

“These violations are crimes against humanity that must be both stopped and punished,” they say. “The culture of impunity within which these dehumanising atrocities have been committed needs to be challenged most vigorously.”

Iraq is not party to the International Criminal Court, the six faiths state, so British diplomats should push for a UN Security Council Resolution that refers this matter to the ICC for investigation and where necessary prosecution.

Alongside the statement, the Muslim Council of Britain (MCB) attacked what it called a “reprehensible organisation,” saying: “We are horrified at the abhorrent murder of reporter James Foley. IS has murdered this man for no reason at all.”

It added: “Each day it seeks to carry out an act more barbarous than the day before, craving the oxygen of publicity to give credibility to their heinous acts. We condemn unreservedly their psychopathic violence, whether on minorities, civilians or fellow Muslims.”

MCB officials said that IS “did not speak for Islam, and has been repudiated by all Muslims”.

“Their message only appeals to those who are easily duped by their twisted message purporting to be Islam,” they said. “We urge the media to refrain from giving them any further undue exposure.”