Deputy Prime Minister Nick Clegg made an unexpectedly strong attack on the Federation of Student Islamic Societies (Fosis) during his speech to the Community Security Trust in Manchester last night.

Speaking about hate speech on campus and general bigotry, the Liberal Democrat leader declared: "But when individuals and groups express attitude that are hostile to Jews, Muslim and non-Muslim alike that cannot be tolerated.

"And we need to be tough and smart in our approach. I've always believed that the general principle that you don't win the fight by leaving the ring, you don't walk away from the battlefield and let bigots spread hate unchallenged. You engage, confident in the power of argument, confident in the power of liberal values to defeat prejudice. Liberalism is muscular, it's not passive.

"I will always defend the right of ministers to take the fight to those who wish to divide our society.

"But of course there are limits. Some organisations we have no choice but to shut down. If we concerned enough about their activities we will, as a last resort, consider proscribing them. We won't provide funding for groups who advocate intolerance, and engaging to change is not the same as endorsing.

"To give you an example, we recently cancelled a recruitment fair aimed at increasing applications by Muslims to the civil service. The proposed partner organisation was the Federation of Student Islamic Societies, an umbrella organisation which has failed to challenge sufficiently terrorist and extremist ideologies.

"If ministers want to meet that organisation, setting out strongly the standards we expect, I'm all for it, but am I willing for Her Majesty's Government to treat them as a credible partner? Absolutely not. Engage to change, yes, endorse and fund, no."