The Archbishop of York John Sentamu has issued an urgent plea for the UK Government to protect religious minorities in Iraq and offer asylum to those in desperate need.
In a statement published on his website, Sentamu condemns the "daily unfolding horrors in Iraq" and insists that Cameron's government must "now take a lead both internationally and domestically to respond".
"The events in Iraq demonstrate a fundamental truth about humanity and its unbridled capacity for brutality," the Archbishop writes.
"I have witnessed first-hand the horrors of brutality and its dehumanising impact upon perpetrators in addition to the untold suffering of victims. Unbridled violence brings untold suffering to victims but also dehumanises perpetrators to such an extent that murder becomes an act of the ordinary instead of a sin against the sanctity of human life."
The plea follows the news that Islamic State (IS) militants killed up to 670 Shia prisoners in Mosul on June 10 in the worst recorded massacre committed by the insurgent group.
Detailing the mass execution on Monday, UN high commissioner for human rights Navi Pillay denounced the "grave, horrific human rights violations" that IS fighters are committing on a daily basis, branding them as amounting to "ethnic and religious cleansing".
"They are systematically targeting men, women and children based on their ethnic, religious or sectarian affiliation and ruthlessly carrying out widespread ethnic and religious cleansing in the areas under their control," Pillay said.
"Such cold-blooded, systematic and intentional killings of civilians, after singling them out for their religious affiliation may amount to war crimes and crimes against humanity."
Sentamu, however, has questioned Pillay's use of language, insisting that "For me this is not ethnic cleansing but human slaughter.
"Holy Writ urges us to overcome evil with good and in circumstances such as those we are witnessing in Iraq, this means actively resisting evil both in terms of protecting the innocent and putting an end to the brutality of the perpetrators."
The Archbishop therefore argues that the UK government must "show leadership" by supporting calls for the creation of a 'safe zone' for minority communities in Iraq.
"As a member of the Security Council the Government has voice and a chance to act. It is essential that they not only take the opportunity to do so but show leadership by encouraging others nation states to do the same," Sentamu writes.
"Domestically the time has come for the Government to show leadership in offering asylum to those at risk of persecution...The Government must show that it has the courage to offer sanctuary to the suffering and to demonstrate that right policies triumph over political calculations."
The statement reveals that the Archbishop has already written privately to PM David Cameron on the matter, and he urges the coalition "to act justly and swiftly in the face of suffering".
"He [Cameron] has already spearheaded the response to those suffering on Mount Sinjar and approved fighters to accompany aid drops. But more still needs to be done," Sentamu declares.
"The time for hard hitting speeches and condemnation has passed. What is required now is action to protect those at risk from slaughter."
The Archbishop is currently undertaking a weeklong fast and prayer vigil for the suffering and persecuted world.
During his vigil of Hope and Trust for the Peace of the World, Sentamu will be praying on the hour every hour from 6am to 6pm until Sunday 31 August, and has invited others to join him in solidarity,