David Cameron: "We believe in respecting different faiths, but also expecting those faiths to support the British way of life"
David Cameron has set out the government's strategy to defeat the "poison" of Islamist extremism.
He pledged to tackle extremist ideology and "the failures of integration" which he said had led to hundreds of Britons joining Islamic State (IS) militants.
Among a number of proposals, the PM promised to allow parents to have their children's passports cancelled if they feared they were at risk.
He also pledged to look at social housing to prevent further segregation.
In a speech in Birmingham on the government's five-year plan to defeat home-grown extremism, Mr Cameron set out four major issues - countering the "warped" extremist ideology, the process of radicalisation, the "drowning out" of moderate Muslim voices, and the "identity crisis" among some British-born Muslims.
He said the focus of his speech was Islamist extremism - not Islam the religion - and that moderate Muslims also hated the "sick world view" of extremists.
"I want to work with you to defeat this poison," he said.
He said the government's strategy included plans to:
He spoke about a lack of confidence when it came to enforcing British values, referring specifically to forced marriage and female genital mutilation.
"No more turning a blind eye on the basis of cultural sensitivities," he said.
Talha Asmal, 17, from Dewsbury, is among hundreds of Britons who have gone to fight for the so-called Islamic State
He said the UK needed to "de-glamorise" the extremist ideology and conspiracy theories used by groups such as IS.
"This is a group that throws people off buildings, that burns them alive... This isn't a pioneering movement, it is a vicious, brutal and fundamentally abhorrent existence," he said.
Keith Vaz, the Labour chairman of the Commons Home Affairs committee, said the government needed to engage with the Muslim communities.
"We need to understand why a few become isolated from their own communities," he said.
BBC home affairs correspondent Daniel Sandford said giving worried parents the power to have their children's passports removed was a concrete step.
At present, children can be made a ward of court and then the local authority can prevent them travelling, or parents can go to the police who could act in certain circumstances, he said.
Our correspondent said the emphasis of Mr Cameron's speech was on the "battle of ideas" but added it could be about 10 years too late.
"The people they have to persuade are the young people who are already, to a degree, lost - and that is a big challenge for the government," our correspondent said.
The stories of those who have died, been convicted of offences relating to the Islamic State conflict or are still in Syria or Iraq.
Mr Cameron said it was not enough for groups to say they opposed IS.
This would be setting the bar for acceptability "ludicrously low", and groups should be expected also to condemn conspiracy theories, anti-Semitism and sectarianism, he said.
"We need to put out of action the key extremist influencers who are careful to operate just inside the law but who clearly detest British society and everything we stand for," he said.
While welcoming aspects of the speech, the Ramadhan Foundation rejected Mr Cameron's use of the term "grievance justification", whereby he said some people blamed the rise of extremism on "historic injustices, recent wars, poverty and hardship".
Chief executive Mohammed Shafiq said the PM's idea that "somehow we're saying foreign policy is an excuse is really offensive".
"If this is the way he wants to engage with the community in the battle against terrorism then he's going to fail," he said.
"He should be talking to a diverse range of organisations, and he's not doing that."
Dr Shuja Shafi, secretary general of the Muslim Council of Britain, said the group agreed with the prime minister that Islamic State's causes must be de-glamorised.
"We worry, however, that these latest suggestions will set new litmus tests which may brand us all as extremists, even though we uphold and celebrate the rule of law, democracy and rights for all," he said.
"Dissenting is a proud tradition of ours that must not be driven underground."
RAF jets have been involved in air strikes against Islamic State targets in Iraq
In his speech, Mr Cameron attacked the National Union of Students for "allying itself" with the advocacy group Cage, one of whose officials earlier this year described the IS militant, Mohammed Emwazi, nicknamed Jihadi John, as a "beautiful young man".
But the NUS responded by saying it would not work with Cage "in any capacity".
The government is expected to set out a wider counter-extremism strategy later this year which will include more legislation.
Police and security services believe at least 700 extremists have travelled to fight with IS militants who have taken control of large swathes of Iraq and Syria, with half since returned and posing a domestic terror threat.
Meanwhile, Defence Secretary Michael Fallon has told MPs that five RAF pilots have been embedded with coalition forces carrying out air strikes against IS in Syria in the past year.
Parliament has approved UK involvement in air strikes in Iraq and Mr Cameron has suggested he could soon seek approval to extend the military action to Syria.