The Reform movement's Senior Rabbi, Laura Janner-Klausner, has spoken at a multi-faith vigil jointly organised by a Muslim charity accused by Israel of links with Hamas.
Islamic Relief Worldwide co-sponsored Wednesday's event on behalf of Iraq's endangered minorities with World Jewish Relief and Christian Aid.
The Birmingham-based Islamic charity has denied allegations of funding Hamas-controlled organisations after being banned by Israeli Defence Minister Moshe Yaalon from operating in the West Bank.
Rabbi Janner-Klausner was joined by Archbishop of Canterbury Justin Welby, Muslim Council of Britain assistant secretary-general Sheikh Ibrahim Mogra and former Faith and Communities minister Baroness Warsi at the vigil outside Westminster Abbey. They urged world leaders to do more to protect Yazidis and other minorities from the threat of Islamic State extremists.
Rabbi Janner-Klausner said she had responded to "an initiative of the UK's three faith-based aid agencies. There are matters on which we might disagree but in order to meet the challenges of today's world, it is vital that we work together where there is common ground".
Our rabbis taught us that no person's life is more valuable than another's
She told the JC: "Our rabbis taught us that no one's blood is redder than another's, that no person's life is more valuable than another's. As faith communities, we will always stand together against the violation of human rights."
WJR chief executive Paul Anticoni said he was "deeply troubled" by the situation in Iraq. "On this occasion, we have united, as humans and humanitarians, to stand by those discriminated against on the basis of their identity."
In a statement, Chief Rabbi Ephraim Mirvis, who was unable to attend owing to prior engagements according to his office, said: "If they do not succumb to forced conversion, the Christian and Yazidi communities of Iraq face an unthinkable choice - stay and be slaughtered or flee and starve. We must help them in their hour of need and guarantee their long term freedom and security."
● Islamic Relief has said it is launching its own investigation into Israeli claims it had funded groups linked to Hamas.
A spokesman for the charity said this week that it "categorically denies" the allegations and was a purely humanitarian organisation. But he added, "As a responsible organisation we are looking into this matter thoroughly to ensure that our processes for aid delivery have been followed."
Islamic Relief said it will not use funds from the Disasters Emergency Committee appeal for Gaza, launched last month, until its review is completed. The DEC is a coalition of charities which include Oxfam and Christian Aid.