Foreign Secretary Philip Hammond today condemned terror apologists who 'seek to excuse' ISIS extremists including Jihadi John. He used speech in London to hit out at the likes of campaign group Cage, which claimed that it was MI5's attempts to recruit Mohammed Emwazi that led to him becoming radicalised and emerge as Jihadi John. Mr Hammond condemned critics who try to 'excuse' the terrorists by pointing the finger of blame at the security services. Philip Hammond condemned critics who try to 'excuse'  terrorists including Jihadi John by pointing the finger of blame at the security services . British citizens who travel to Iraq and Syria to fight against ISIS could face prosecution if they return. Philip Hammond said that parents and schools have a responsibility to help prevent young people from travelling abroad to take part in the conflict in Syria and Iraq. Asked what the authorities' response would be to Britons who take up arms against IS, the Foreign Secretary said: 'The simple, legal answer is that anyone conducting irregular fighting activity overseas is subject to British legislative sanction. 'That is unlawful activity and can be dealt with on their return to the UK.' The parents of three London schoolgirls believed to have entered Syria with the aim of joining IS - Shamima Begum, 15, Kadiza Sultana, 16, and 15-year-old Amira Abase - are later due to appear before the House of Commons Home Affairs Committee, alongside the ambassador of Turkey. Cage sparked outrage last month with its attempts to justify Emwazi's brutal killings of ISIS hostages. In an extraordinary press conference, the group's research director Asim Qureshi said Kuwait-born Briton Emwazi was a 'beautiful young man', 'extremely gentle' and 'the most humble young person that I ever knew'. The 32-year-old blamed British security services for Emwazi's radicalisation, saying he had tried to fit in but had been made to feel like an 'outsider'. Today Mr Hammond vehemently rejected the idea that the actions of Emwazi and other ISIS murderers can ever be justified. He said: 'The exposure of the alleged identity of one of the most murderous ISIL terrorists over the last few weeks has seen some seeking to excuse the terrorists and point the finger of blame at the agencies themselves. 'We are absolutely clear: the responsibility for acts of terror rests with those who commit them. But a huge burden of responsibility also lies with those who act as apologists for them.' In a rare speech on the intelligence agencies, Mr Hammond will mount a strong defence of their work saying that it was only their 'brilliance' that had kept Britain safe in the face of the continuing terrorist threat. The agencies have also faced criticism over the fact that Emwazi was allowed to travel to Syria - where is believed to have carried out the brutal beheadings of a series of western hostages - even though he had be known to MI5 since 2008. Speaking at the Royal United Services Institute in London, Mr Hammond - who is responsible for MI6 and GCHQ - said that agencies are currently facing an 'unprecedented' level of challenge in the face of a wide range threats from around the world. 'The sheer number and range of cases, old and new, amounts to the greatest challenge to our collective security for decades and places unprecedented demands on those charged with keeping us safe,' he said. 'Warped' Cage's research director Asim Qureshi (left) at a press conference about Jihadi John last week . Prime Minister David Cameron dismissed as 'nonsense' the suggestion that jihadis like Emwazi had been radicalised by their contact with security services. Mr Cameron told LBC radio: 'The fact is we face a terrorist threat in Britain. That is the opinion of the experts who advise me and set the threat level. 'Our police and security services have a very important role to play to find out about people that could do us harm and to step in and prevent them from doing that. 'Of course we need to work with communities to do that - and we do. 'But I totally reject the idea that police or security service tactics have somehow radicalised people. That is, I think, nonsense.' Campaign group Cage sparked outrage last month with its attempts to justify Emwazi's brutal killings of ISIS hostages. In an extraordinary press conference, the group's research director Asim Qureshi said Kuwait-born Briton Emwazi was a 'beautiful young man', 'extremely gentle' and 'the most humble young person that I ever knew'. The 32-year-old blamed British security services for Emwazi's radicalisation, saying he had tried to fit in but had been made to feel like an 'outsider'. He said that while in the past they had simply had to focus on 'ideologically-driven expansionist states' they now had to deal with international terrorist groups and state-sponsored aggression as well as self-radicalised, 'lone wolf' terrorists. 'The emergence of groups such as Boko Haram in Nigeria and (IS) in Syria, Iraq and Libya, simply serves to underline the pace with which the threats to our safety and security from this source are evolving,' he said. 'It is only thanks to the dedication, and in many cases the brilliance, of our intelligence officers that we have succeeded to detect and contain these threats.' At the same time he pointed to the renewed threat to international order posed by Russia after years of re-engagement with the West following the end of the Cold War. 'We are now faced with a Russian leader bent not on joining the international rules-based system which keeps the peace between nations, but on subverting it,' he said. 'President (Vladimir) Putin's actions - illegally annexing Crimea and now using Russian troops to destabilise eastern Ukraine - fundamentally undermine the security of sovereign nations in Eastern Europe.' He said that the 'clandestine nature' of the threats- from weapons systems developed in secret to covert plotting by terrorists - underlined the need for Britain to maintain a 'highly effective, secret capability' to identify, monitor and act against them. 'As the range of threats gets bigger, so the pace of technological change with which the agencies must keep up is getting faster, making their central task of keeping us safe ever more demanding,' he said. 'We must respond decisively and positively to the public and parliamentary debate about the powers required by our intelligence agencies to do their job in a changed technological environment - and in doing so draw a line under that debate so that the agencies can get on with the job of keeping this country safe.'
Foreign Secretary condemns critics who try to 'excuse' the terrorists . Campaign group Cage blamed MI5's attempt to recruit Mohammed Emwazi . They said it led to him becoming radicalised and emerging as Jihadi John . Hammond says responsibility also lies with those who act as apologists .