RNA - The imams -- from some of the notorious recruiting grounds for IS -- condemned Internet companies for letting the web become a "safe haven" for terrorists.
The religious leaders represent cities such as London, Leicester, Leeds, Lancashire, the West Midlands and Buckinghamshire.
They warned that the failure to stamp out "readily available" extremist content on social media sites is "undermining" community cohesion.
IS has used social media to recruit foreign fighters in the Middle East, and for propaganda.
According to The Sunday Times, this group is spearheading a new campaign that allows ordinary Muslims to report extremist websites that carry beheading videos, terrorist training manuals and sermons by preachers of hate.
A new website, called Imams Online, is being backed by both Sunni and Shi'ite imams from communities across the UK to prevent young Muslims leaving their homes to fight in Iraq and Syria.
Shaukat Warraich, editor of the website, said: "From images of terrible violence and murder to preachers sowing the seeds of hatred, each and every example of this harmful content has the potential to hurt us all.
"This is a plea from representatives of all our communities to the public and Internet and social media companies to act to help keep us safe from extremist content. The Internet can no longer be freely used by terrorists and those that would cause division and espouse hatred."
The campaign is being backed by Maulana Shahid Raza of the British Muslim Forum, a senior imam at Leicester central mosque, and Hafiz Ghulam Rasool, director and principal of the Hazrat Sultan Bahu Trust in Birmingham.
Other imams who signed up included Qari Muhammad Asim of the Makkah Mosque in Leeds, Hafiz Zaheer Shabir of the Bristol Council of Mosques, Sahibzada Ghulam Jeelani of the Wycombe Islamic Mission, and Abdul Hameed Qurashi of the Lancashire Council of Mosques.
Hope Not Hate, the Active Change Foundation and Upstanding Neighbourhoods have also joined hands with the campaign.
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