Online video giant YouTube has been condemned for failing to take down extremist content including films praising Adolf Hitler and Taliban propaganda.
An extensive study of Islamist and far-right extremist material shared on the website found more than 120 videos were not removed even after they had been flagged to the site's administrators.
Yvette Cooper, chairwoman of the influential Commons Home Affairs Select Committee, said it was "simply unacceptable" that some content remained live weeks after being reported.
The Labour MP commissioned the study by foreign policy and security think tank the Henry Jackson Society, which involved monitoring YouTube over almost three months.
During the study, researchers flagged up 107 Islamic extremist videos and 94 examples of far-right content.
But 61 of the far-right videos and 60 of the Islamic extremist posts remained online for viewers to watch.
A video featuring praise of the Nazi leader over images of Jewish families being taken to concentration camps, was flagged on August 1 but was still live on September 18.
Promotional material from the Taliban was flagged on August 29 but still available on September 18.
Other videos still available despite being reported included footage of a child singing over images glorifying terrorism, a man filmed slapping a Muslim teenager with bacon while shouting "Isis scum" and a video of burning buses celebrating the deaths of Shia Muslims.
Ms Cooper said: "It is simply unacceptable that YouTube are taking so long to remove material that contains images and content that glorify extremist violence.
"YouTube have promised to do more, but they just aren't moving fast enough. Google, which owns YouTube, is one of the richest and most innovative companies on the planet. They have the resources and capability to sort this and they need to do so fast."