Mark Rowley (pictured) called for police, social workers and family court judges to step in and protect the vulnerable families of twisted extremists

Violent Islamists should be treated like paedophiles and have their children taken away from them, Britain’s top counter terrorist officer said last night.

Mark Rowley called for police, social workers and family court judges to step in and protect the vulnerable families of twisted extremists.

The Scotland Yard chief officer said terrorist propaganda and sexual abuse were ‘equally wicked’ forces for children.

But, he warned, extremists were often left to care for impressionable youngsters despite convictions for violence and spreading hate.

In a keynote speech, Mr Rowley also warned against underestimating the threat of the Far Right as he revealed four plots were foiled last year.

Delivering a comprehensive assessment of the enduring terrorist threat on the eve of his retirement, the top police officer:

Called for the British Islamic State killers dubbed ‘The Beatles’ to face justice, adding: ‘Locking them up and throwing away the key would be a good idea.’

Urged web giants to do more to stop terrorists plotting attacks, spreading vile propaganda and hiding behind the anonymity of the dark web.

Branded Far Right and Islamist extremists a ‘toxic combination’ who feed off each other to spread hatred and division.

Painted a stark picture of the challenge facing police and MI5, with more than 600 ongoing investigations into at least 3,000 suspects.

Mr Rowley is stepping down from the Metropolitan Police just months after leading the nation’s response to five catastrophic terrorist attacks.

The Assistant Commissioner paid tribute to his emergency service colleagues and members of the public who acted with ‘compassion, determination and heroism’.

But he warned that the threat of Islamist terrorism was here to stay despite IS’s loss of huge swathes of territory in Iraq and Syria.

Speaking ahead of a valedictory speech to the Policy Exchange think-tank, he said terrorist arrests increased by a third last year.

Mr Rowley criticised pro-Islamist groups, including Cage, and admitted the authorities have sometimes been too ‘tolerant of intolerance’.

He warned that firebrand Islamists and a resurgent Far Right often want to sow the same division, fear and mistrust.

Mr Rowley called for the British Islamic State killers dubbed ‘The Beatles’, a group which included Jihadi John (real name Mohammed Emwazi, pictured), to face justice

Mr Rowley compared the danger the children of some Islamists face to that of paedophiles, saying more could be done to protect them.

He said around 100 children have been safeguarded since the start of the conflict but the system must be improved.

‘The police, social services and the courts have a lot of experience of safeguarding work and taking cases through the family courts where there are paedophile parents,’ he said.

‘If we have got parents showing propaganda material does that pose a risk to children that should be treated in the same way as parents of paedophiles? It is the level of risk.

‘If you know parents are interested in sex with children, or if you know parents believe that people of their faith or their belief should hate everybody else and corrupt children for it, for me those are equally wicked environments to expose children to.’

Turning to the fate of ‘The Beatles’, Mr Rowley said they must be put on public trial but declined to say in which country.

El Shafee Elsheikh (left) and Alexanda Kotey, members of the notorious execution group nicknamed ‘The Beatles’, were detained by US-allied Kurdish militia fighters in January

This month, the final two members of the notorious terror cell were captured close to the Syrian border with Iraq.

The gang’s leader, Mohammed Emwazi, better known as ‘Jihadi John’, was killed in a 2015 drone strike. The fourth is in a Turkish prison.

Mr Rowley said: ‘The people that have done the most gravest things overseas, the ones that do not fight to the death, we would all like to see them never able to do anyone any harm ever again.

‘Locking them up and throwing the key away would be a great idea, it depends on the jurisdiction’s legal framework, whether there is evidence to meet everyone’s assumptions.’ Mr Rowley said the ability of extremists and terrorists to ‘ply their trade through the internet’ remains a matter of ‘grave concern’.

He said it ‘cannot be right’ that someone can be radicalised, exchange encrypted messages with terrorists, research targets without a trace and buy bomb materials - all online.

But he added the biggest internet companies, mostly based in the US, have improved their response and he hoped smaller firms will follow suit.

He compared the efforts of Google, Facebook and Twitter to the reluctance of the banking sector to help chase out dirty money when police first asked for help.

Mr Rowley is stepping down from the Metropolitan Police just months after leading the nation’s response to five catastrophic terrorist attacks

The top officer said companies are finally ‘rolling up their sleeves’ and that progress will be made by ‘persuasion and regulation’.

Asked whether the authorities have been too ‘politically correct’ to single out some groups for fostering extremism, Mr Rowley said it was a ‘sensitive’ area.

‘I think there are times when we have been tolerant of intolerance. That is a phrase other people have used as well,’ he said.

‘This requires careful handling. If the State is over assertive in tackling issues you can aggravate problems. If you are overly cautious you allow things to fester and grow.

Mr Rowley called on the public to join the struggle against terrorism, saying there are a ‘million things’ people can do to counter extremist views.

‘It is about being tolerant and united members of society, not falling for some of the nonsense with which others try to create fear and discord’ he said.

Potential successors to Mr Rowley, who steps down next month after a 31 year career, including his colleagues Helen Ball and Neil Basu as well as West Midlands Chief Dave Thompson.