Internet giant Google has said that its video-sharing website YouTube is so inundated that it makes it tough for staff to filter all "terror"-related content.
Google said the volume is complicating the struggle to halt the publication of terrorist propaganda and hostage videos.
Verity Harding, Google public policy manager, said on Wednesday that about 300 hours of video material is being uploaded to YouTube every minute, making it a heavy workload for the company to filter all images.
Harding spoke at a European Parliament meeting of the Alliance of Liberals and Democrats for Europe (ALDE) liberal group on a counter-terrorism action plan.
She said that "to pre-screen those videos before they are uploaded would be like screening a phone call before it's made."
The European Union's counter-terror chief said it is time to help companies to contain the security risk by having experts from member states flagging terror-related content.
"We have to help them, and refer to them, and signal content," Gilles De Kerchove said. "Each member state should have a unit with people trained to do that."
On YouTube, users can highlight problem videos and have them reviewed by a member of staff.
When a Scotland Yard unit recently told Google about material that did not comply with the company's own guidelines, De Kerchove said 93 percent of that content was removed. But when individuals flag up problems only a third of it is taken down.
Detecting violent, extreme and racist material is a mammoth task. But concerted, targeted warnings from organised groups work best, the meeting was told.
"There are community groups and others who do this on a larger scale and they're incredibly helpful to us,'' Harding said.
Neither the big Internet companies nor the European Union appear willing to take on a legal battle to enforce their removal.
"We can contemplate legislation but I suspect it would be an awfully monumental exercise," De Kerchove said.