Britain's Prime Minister David Cameron has launched an investigation to see whether extremists have infiltrated Britain's schools, hospitals and local councils.

The review will assess the "risked posed by entryism" in the NHS, education institutions, the civil service and local authorities in the wake of the issues raised by the Trojan Horse scandal, where schools in Birmingham were targeted by radical Islamists.

School teachers are already being trained to spot the signs of radicalization of children and NHS staff have been trained to check employees joining the health service.

The review will report back in 2016 and will set out the risk to public institutions of people seeking to gain positions of power and influence to forward their extremists views.

It will advise on how best to safeguard them with improvements to "governance, inspection and whistle-blowing mechanisms."

The details are contained in the Government's wide-ranging counter terrorism strategy, which has been released today.

Launching the strategy on Monday Cameron also announced that will see extremists treated like pedophiles and banned from working with children and vulnerable people.

In a speech, Cameron warned extremism was "one of the biggest social problems we need to overcome".

He said: "A key part of this new approach is going further to protect children and vulnerable people from the risk of radicalization by empowering parents and public institutions with all the advice, tools and practical support they need."

And he added: "We know that extremism is really a symptom; ideology is the root cause - but the stakes are rising and that demands a new approach.

"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."

Other measures contained in the strategy will allow parents to have their children's passports revoked if they are at risk of joining extremist groups in Iraq and Syria.

The system has already been trialed but will now be extended to include 16 and 17 years olds.

Home Secretary Theresa May said that a small number of parents had applied for their children's passports to be seized.

She told Sky News: "We would say that somebody who has been convicted of a terrorism offence ... would be automatically barred from working with children or vulnerable adults.

"That's just one measure in what is a very wide-ranging counter-extremism strategy that we are launching today ... we do face an unprecedented threat from extremists.

"Groups like ISIL can send through the internet their message of hatred into family homes. We see men and women - and indeed whole families - going out to Syria. I think that shows us that we need to step up our action on counter-terrorism."

The Home Office says that in the past year 50 under-20s have been arrested for terrorist offences and it is a "growing trend".

In February, three East London schoolgirls fled to Syria to join IS. Their families later confirmed two of them were married to militants in the group.

The measures will also see radical preachers stopped from posting material online.

The Prime Minister said on Sunday that groups tackling extremism in the UK are being given $5.6m this year to help their work in preventing the "seed of hatred being planted in people's minds".

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