We are welcoming back our eight undecided voters tonight. Here's what they think on security...

Mark Urban
Newsnight Defence and Diplomatic Editor

Image source, Getty Images

Theresa May’s intervention highlights a key question often missing in the Brexit debate: not what the EU can do for us, but what the UK can do for the Union. The Home Secretary highlighted the new effort to get a Passenger Name Record system operating across Europe, saying, “without British leadership and influence, a directive would never have been on the table, let alone agreed”.

This exchange of information about people travelling, abbreviated PNR, is considered essential in the counter terrorist field but, remarkably, does not yet exist in most European countries. Britain has had a PNR database operating since 2012 and has spearheaded the push for the system’s extension across the EU – something that has been given added impetus by the Brussels and Paris attacks.     

There are many other areas where the UK is a net contributor to European security, in the view of many practitioners (in the military or security sector) I’ve spoken to. Whether it’s a close vote on the extension of economic sanctions against Russia for its actions in Ukraine, or the organisation of an anti-piracy naval force, the UK can make a difference in driving forward the larger group. This chimes in with President Obama’s statement about EU membership , externalmagnifying rather than diminishing British influence.

Those who would prefer to leave the EU counter that key Nato and intelligence relationships would remain unchanged, arguing also that Britain’s capabilities would continue to give it influence over European security. That’s not a point most of the ‘Remainers’ would seriously dispute. Rather they say that it’s harder to exert security leadership when you’re no longer at the table, and that weaker or less effective security policy making in the EU would ultimately rebound to Britain’s cost.       

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The Home Secretary appeared today to find a third way between Brexit and Bremain, when considering the impact of EU membership on national security.

She stayed nominally loyal to her party leadership, saying that "remaining a member of the European Union means we will be more secure from crime and terrorism".

But she managed to make some fairly eurosceptic noises by calling for a British exit from the European Convention on Human Rights (which she argues has had a much more detrimental effect on UK security than the EU, by stymieing attempts to deport people like Abu Hamza and Abu Qatada).

Cynics may suggest that she is attempting to appeal to as many future voters in a Conservative leadership election, external as possible.

We have a simple question this evening - is the EU aiding our security? Or not? 

"I cannot lie. This isn't easy. I have been a closet Euro-sceptic for most of my adult life. An internationalist to the core, I nonetheless shared the concerns of so many people in Britain and Europe about the apparent lack of accountability of the mighty institutions of the European Union and the smallness we can feel as individuals so far from Westminster, let alone Brussels.

"Which is why the Newsnight debates have focused my mind and diverted me away from understandable emotions about sovereignty and Europe towards practical debate about whether we might be wealthier, happier, safer and more sustainable in or out.

"As the former director of Liberty, many of my concerns about the EU came from a civil liberties perspective. Perhaps the EU arrest warrant had made it too easy to waft people around Europe and information sharing has been too easy at a cost to personal privacy. But from a security perspective, I cannot ignore the ultimate benefits of  the closest possible cooperation against truly globalised threats whether against international criminals, tax evaders, hackers, kidnappers or terrorists. Security can obviously be approached from two perspectives: Batten down the hatches or work with your friends. There are arguments either way. 

"But in the end, globalisation is now a reality and not a choice. What happens "over there" has such an immediate effect on our lives "over here" that the path of easier intelligence, information and strategy sharing is vital. The threats to security, not least cyber-threats, are international. So must be the response. With greater sharing must come greater trusts and safeguards and like the Leader of the Opposition, I want to see a reformed EU that treasures common values as well as shared markets. But in the end I choose to build security with my neighbour's and not to lock my doors and hope for the best."

Shami Chakrabarti was director of Liberty from 2003-2016

"Britain’s security would be strengthened if we left the EU. Inside, we can’t really control who enters if they are EU citizens, unless we can demonstrate that they pose an immediate threat to us. That means large numbers of jihadists returning from fighting with the Islamic State can come to Britain and we can do nothing about it. Our intelligence and security services are already stretched thin trying to monitor terrorist suspects from our own country.

"In too many cases nor can we throw out people who pose a direct threat to us – wherever they’re from in the world - because our ministers and courts can be over-ruled by the European Court of Human Rights. While we remain in the EU we have to submit to the jurisdiction of that court, even though it’s separate to the EU.

"Despite scaremongering by Remainers, intelligence-sharing and security cooperation would not be weakened if we left the EU. All sharing of significant intelligence is bilateral now and will remain so – it is not coordinated through EU mechanisms. In fact our closest intelligence partner, by far, is not even an EU member – the United States.

"On all aspects of security we have at least as much to give to our European allies as they can give to us. We have the best intelligence and police services in Europe. Why on earth would European countries try and weaken this cooperation just because we left the EU? If they did, they would be putting their own citizens at unnecessary risk."

Richard Kemp is a senior miltary officer and former commander of the first Task Force in Helmand

How important is security for you in deciding how you will vote in the EU referendum?

Do you have questions on security and the EU that we should put to our guests tonight?

Let us know by leaving a comment on our Facebook page, external or tweeting us @BBCNewsnight , externalusing #newsnight

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Would the UK be safer in or out of the EU? 

Read this primer from Mark Urban here

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Here are some useful primers from key defence and security players on both sides of the debate:

"Britain’s military standing would not suffer after Brexit", external - Anand Menon, in the FT, argues that the UK would actually find it easier to work with European allies *outside* the EU.

"Brexit would be bad for security in Europe warns Nato chief'", external - Nato Secretary General Jens Stoltenberg warns against Brexit.

"Brexit would not damage UK security", external - Ex-MI6 head Sir Richard Dearlove says that from a national security perspective, "the cost to Britain would be low".

"Richard Dearlove is very wrong: leaving the EU would weaken British security'", external - Dame Pauline Neville-Jones (former Security Minister and ex-chair of the Joint Intelligence Commitee) fires back at Sir Richard.

Ian Katz
Newsnight Editor

Image source, Getty Images

What would Vladimir Putin want? That's the question many in the Remain campaign would like you to ask as you enter the voting booth on 23 June. 

They are confident that the answer to the question is "Brexit" and that that should tell us all we need to know about whether leaving the EU would make us more or less safe in the world. 

The Leave camp would rather you thought about the two men who entered Europe posing as refugees on the Greek island of Leros, crossing several European borders before bringing terror to the streets of Paris in November. Or Salah Abdaslam, who slipped across the border back to Belgium after taking part in the attacks. 

Their message: with its permeable borders and patchy anti-terror efforts, how can the EU possibly make us safer? 

We'll doubtless hear variations on both arguments tonight, in the third of our special programmes about the big issues in the EU referendum. We'll also try to get to the bottom of some of the big arguments around European Arrest Warrants, intelligence sharing and whether the EU gets in the way of us kicking dangerous people out of the country. 

To help us we've assembled a formidable panel of experts - including Europol chief Rob Wainright and former Met anti-terror chief Richard Walton. Sadly Vladimir Putin couldn't make it. 

Tonight's topic is security – would the UK be safer in the EU or out?

In the third of our EU specials, Evan Davis is joined by two key players from either side of the debate, a panel of experts, and a group of undecided voters. 

Tonight's programme starts at 10.30pm on BBC Two as well as right here at the top of this page. 

We'll be live blogging from 10pm with extra background, insights and analysis. See you then...  

While you're waiting, why not take a look at our recent EU Referendum live blogs...

Economy: Would we be off in or out of the EU?

Sovereignty: Who really rules the UK?