LONDON — Britain on Monday announced new measures intended to prevent the radicalization of young Muslims, stoking a debate about how aggressively the government can confront extremist ideology without alienating the moderate voices best placed to combat it.
Publishing a new counterextremism strategy, the government outlined a range of plans, including moves to prevent radical material from being posted online and to ban anyone who expresses conviction to commit terrorist crimes or extremist activities from working with children.
A panel will examine the application of Shariah law in Britain, and another will seek to ensure that schools, colleges, local authorities and health services are protected against infiltration by extremists.
Prime Minister David Cameron has described the battle against Islamic extremism as one of the great struggles of his generation, and on Monday he argued that combating it had also involved promoting national values such as tolerance and an understanding of different faiths.
“We know that extremism is really a symptom; ideology is the root cause. But the stakes are rising, and that demands a new approach,” he said.
“So we have a choice: Do we choose to turn a blind eye, or do we choose to get out there and make the case for our British values?” Mr. Cameron added.
As in other countries in Europe, a steady flow of young people has left Britain for conflict zones to support jihadist groups. More than 700 Britons are thought to have traveled to support or fight for jihadist organizations in Syria and Iraq, with many joining the Islamic State, also known as ISIS, ISIL or Daesh.
Mr. Cameron’s office said that of 338 recent arrests related to counterterrorism, 157 were linked to Syria and 56 involved people younger than 20.
The government says the new strategy, which covers all forms of extremism, is intended to disrupt those with extreme views, pursue those responsible for radicalization and address some of the social conditions that have allowed extremism to flourish.
But critics say they worry that the term “British values,” used by Mr. Cameron, may alienate moderate forces in the community and that some of the new measures may be seen as heavy-handed and exacerbate the sense of resentment among young Muslims, which is itself a driver of radicalization.
Shuja Shafi, the secretary general of the Muslim Council of Britain, said in a statement that the strategy continued “down a flawed path” and was “based on fuzzy conceptions of British values.”
“It risks being counterproductive by alienating the very people needed to confront Al Qaeda- or Daesh-related terrorism: British Muslim communities,” Mr. Shafi said.
Highlighting fears that mosques, where extremist meetings are said to have taken place, might be closed, Mr. Shafi argued that there were “McCarthyist undertones in the proposal to create blacklists and exclude and ban people deemed to be extremist.”
The Home Office, which is responsible for Britain’s internal security, said the strategy did not include a specific proposal to close mosques, although it did promise to push legislation to create new powers for fighting extremism.
These would make it possible to “ban extremist organizations that promote hatred and draw people into extremism; restrict the harmful activities of the most dangerous extremist individuals; and restrict access to premises which are repeatedly used to support extremism,” the strategy document said.
The document also promises to clamp down on the dissemination of extremist messages on social media, partly by creating a group involving the “industry, government and the public.” The government wants to “support a network of credible commentators who want to challenge the extremists and put forward mainstream views online.”
And parents would be able to ask the government to seize the passports of 16- and 17-year-olds thought to be considering travel to Syria and Iraq, extending an existing right for parents to request the cancellation of travel documents for those under 16.
Andy Burnham, who speaks for the opposition Labour Party on home affairs, said in a statement that he would seek to ensure that “in this difficult area, the government gets the balance right” and does not go beyond that.
“This summer, David Cameron failed to strike that balance by implying that the whole Muslim community ‘quietly condones’ extremism,” Mr. Burnham said before Mr. Cameron’s remarks. “He should use today’s speech to correct that suggestion and set the right context for the difficult decisions that lie ahead by building bridges with the Muslim community.”
“If he’s not careful, they could have the opposite effect and fuel resentment, division and a sense of victimization,” he continued. “The government must proceed with the utmost caution, and Labour will watch carefully to ensure the correct balance is achieved.”