The rise of the so-called Islamic State in Syria and Iraq is one of the most serious and dangerous issues we have had to face since we came into Government. Whatever we call this organisation – IS, ISIL or Da’ish – we can’t ignore their brutal activity. The graphic and disturbing images of violence coming from Syria and Iraq show the barbaric way this extremist group has perverted the Muslim faith.

We also need to face up to the reality that this group has publicly announced its desire to bring its murderous ideology to the streets of Britain. The murder of Drummer Lee Rigby is a stark example of the potential threat from extremist ideologues. It is estimated that around 500 British citizens have gone to Syria and Iraq to fight for ISIL and other military groups. Around half have returned and others will continue to do so. This presents a new and unique challenge to the UK security services and police, and earlier this year the Joint Terrorism Analysis Centre, run by MI5, raised the threat level from ‘substantial’ to ‘severe’. This means that an attack in the UK by violent extremists is highly likely.

Because of this threat, we have had to look carefully at potential gaps in existing legislation and listen to the advice of the police, security services and other experts, such as David Anderson QC, the independent reviewer of counter-terrorism legislation. I want to make clear that we have not rushed into a knee-jerk response, as Labour did with its attempt to impose 90 day detention without trial. The Liberal Democrats have made sure that the new Counter Terrorism and Security Bill, published today, is proportionate, evidence-led and protects an individual’s civil liberties as well as improving the safety of all British citizens.

The new legislation will help us to counter radicalisation, making sure that schools, colleges and probation providers help to prevent people being subverted by dangerous extremist groups. We will also make sure that British insurance firms are not inadvertently funding terrorist groups by paying out ransoms. We are improving our border security, including formalising the existing process where airlines provide the UK with information about people travelling on flights to the UK.

The Bill will include powers temporarily to seize the passports of those who attempt to travel abroad to fight for ISIL and other terrorist groups. But, to stop this power being misused, we have made sure that any decision will be subject to a 72 hour check by a senior police officer, followed by a full review by a judge after 14 days. This will give us the opportunity to speak to someone and hopefully divert them away from extremist activity.

A much debated issue has been how we deal with those British citizens who have already gone to fight in Iraq and Syria. Some of those people may have committed crimes and need to be prosecuted, but others may admit they were naïve and regret the decision to travel to the conflict zone. That is why we are introducing a Temporary Exclusion Order that allows us to make sure that suspected foreign fighters travel back to the UK without presenting a risk to the public. This is not a power to make people stateless or ban British citizens from entering the UK. It is a power to manage a very real risk, make sure that we can engage with those who have been fighting abroad, and try to prevent crimes being committed if they return to the UK.

Another part of the Bill which will undoubtedly attract scrutiny are the changes the Government is proposing to make to Terrorism Prevention and Investigation Measures. We have listened to the advice of David Anderson QC, who has proposed the limited introduction of location restrictions. David Anderson is a liberal lawyer, with an impeccable record of analysing counter-terrorism policy. That is why we had to look carefully at his proposals. This is not the return of Control Orders, which could put someone under punitive house arrest for an unlimited amount of time. Instead it is a balanced list of reforms including, crucially, raising the legal burden of proof and creating a tighter definition of terrorism. At present the Home Secretary only needs a reasonable belief that someone may commit or support an act of terrorism. We will change this so that the decision will be taken and verified by a court on the higher ‘balance of probabilities’ test. I know that Lord MacDonald QC, the former Director of Public Prosecutions and one of our own peers, has looked carefully at David Anderson’s proposals and agrees that they are an improvement.

Finally, we are legislating to ensure that communication service providers keep a record of IP addresses. This is simply a way of identifying which computer or smart phone is using the internet and it does not require the retention of private data, such as the websites you visit. As Mark Pack has explained, this is akin to giving internet-enabled devices a listing in the phone book, or way of identifying them if they come up as part of a criminal investigation. Liberal Democrats have always supported this and can rest assured that it is not the return of the so-called ‘Snooper’s Charter’, something we continue to oppose. Instead, it is a sensible proposal which will improve public safety. But, as part of this, we will also be establishing the independent Privacy and Civil Liberties Board. This is based on the American body which holds the government to account for its laws, regulations and activities related to counter-terrorism.

So in conclusion, by carefully examining the specific threat posed by the so-called Islamic State, we have produced draft legislation that provides sensible and proportionate tools to tackle the threat of violent extremism and terrorism. I have no doubt that both Houses of Parliament will need carefully to scrutinise these proposals. But, as the party of civil liberties and now a party of government, I am confident that the Liberal Democrats are on the right track, and that we are doing the right thing.