Facebook was under increasing fire tonight for allegedly hosting pages promoting hatred against Jews after a report found that militants and hate groups were increasingly using social networking sites as propaganda tools to recruit new members.

The Simon Wiesenthal Centre, the Jewish human rights group named after the renowned Nazi-hunter, said it has found a 25 per cent rise in the past year in the number of "problematic" social networking groups on such sites as YouTube. A third of the new postings were on Facebook alone.

The centre said it had identified more than 10,000 websites, social networking groups, portals, blogs, chat rooms, videos and hate games that promoted racial violence, anti-Semitism, homophobia, hate music and terrorism.

It said another site for the white supremacist group Stormfront, which it said was generally considered the first online hate site starting in 1995, used its Facebook page to connect thousands of visitors to their main website. Stormfront's founder Stephen Donald Black, a former Ku Klux Klan grand wizard, is on the list of 16 extremists banned from entry into the UK by the Home Office.

"Every aspect of the internet is being used by extremists of every ilk to repackage old hatred, demean the 'Enemy,' to raise funds and, since 9/11, recruit and train Jihadist terrorists," it said in a statement.

Facebook has seen growing protests over a number of groups on its site. It has removed two Holocaust denial groups, on the grounds that comments from members violated the site's terms of service by promoting hate. The two groups "Holocaust is a Holohoax" and "Based on the facts ... there was no Holocaust" were taken down over the weekend after protests from bloggers.

Facebook said that it was allowing other Holocaust denial groups to remain up because it did not want to restrict free speech over a controversial issue and they did not cross the line into hate speech. A spokesman said that "the mere statement of denying the holocaust is not a violation of our terms".

The company said it had consulted experts but keeping the world more open was better than censorship as a way of combating ignorance or deception. It said it was monitoring Holocaust denial groups carefully.

Facebook's statement of rights and responsibilities says that users may not "post content that is hateful, threatening, pornographic, or that contains nudity or graphic or gratuitous violence". Under these rules Facebook has removed numerous pictures of breastfeeding babies if the mother's nipple is showing, a decision which has also provoked controversy.

The Simon Wiesenthal Centre said it had been monitoring the use of the internet by extremists for more than a decade. It said the rise of social networking sites such as Facebook had accelerated the spread of racist and bigoted views in recent years. "This user-generated material increases the viral spread of extremism online and aids in increasing the social acceptability of hate in mainstream discourse." it said. "By creating an environment where users are equal participants in the web, all editorial functions are removed and expressions of hate can easily flow unchallenged."

It added that Facebook officials had met with its experts and pledged to remove sites that violate its terms of usage. Other groups have created online games such as Special Operation 85 - Hostage Rescue, a game created by an Iranian organisation in which the player has to locate nuclear scientists taken hostage by Americans in Iraq and believed to be held in an Israeli prison.

The most often targeted groups on the internet according to the report include Jews, Catholics, Muslims, Hindus, gays, women and immigrants.

Facebook said in a statement: "Many of the groups or pages that were shown to us by the Simon Wiesenthal Centre earlier this year as part of their study had already been removed under Facebook’s rules. We are committed to continuing this practice, and to working with those who fight hate like the Simon Wiesenthal Centre."

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