Britian's Prime Minister David Cameron says his country cannot tolerate Islamic extremism.

In a speech on terrorism to the annual Munich Security Conference Saturday, Cameron warned that Britian's multiculturalism policy has created segregated communities where Islamic extremism thrives.

"We have even tolerated these segregated communities behaving in ways that run counter to our values," Cameron said. "We have encouraged different cultures to live separate lives, apart from each other and the mainstream."

Britain has become one of Europe's most active bases for terrorist plots.

He said Britain had found that many convicted terrorists had initially been influenced by so-called "nonviolent extremists" - people who aren't involved in encouraging plots, but denounce Western politics and culture - before going on to carry out violence.

Cameron also reached out to the rest of Europe, calling on countries to "wake up." He said that terrorism can't be defeated by simply taking outside actions, but that European countries need to pay attention to what's happening in their own borders.

"If we are to defeat this threat, I believe it's time to turn the page on the failed policies of the past," Cameron said. "Instead of ignoring this extremist ideology, we - as governments and societies - have got to confront it, in all its forms."