'ISIS pose a greater threat to Britain than we have known before': Prime Minister warns an attack on the UK is now 'highly likely'

The Prime Minister's remarks came after the official threat level was raised from substantial to severe - the second highest - amid growing fears over extremists returning from Iraq and Syria. Mr Cameron (pictured speaking in Downing Street today) said ISIS now posed a 'greater and deeper threat to our security than we have known before'. The PM said terrorism was 'the most important issue facing this country today'. He also announced that new laws will be passed to make it easier to remove extremists' passports if there are concerns they will travel to the Middle East to join ISIS. The Prime Minister's remarks came after the Home Secretary Theresa May stressed that there is no information to suggest an attack is imminent, but warned: 'We face a real and serious threat in the UK from international terrorism.'