Britain risks becoming 'a safe haven for Europe's criminals', Clegg warns Cameron in row over clawing justice powers back from Brussels Lib Dems threaten to block Conservative demands to opt out of more than 100 EU measures if European Arrest Warrant is dropped Nick Clegg meets campaigners in favour of cross-border police powers Deputy prime minister Nick Clegg is demanding Britain remains signed up to the European arrest warrant Britain risks becoming a 'safe haven for Europe's criminals' if it withdraws from cross-border police powers, Nick Clegg warned today. The Deputy Prime Minister is demanding Britain remain signed up to the European Arrest Warrant or he will veto Tory demands to opt out of more than 100 other justice measures. The stand-off risks a major Coalition row as both parties seek to appeal to their grassroots in the wake of the Eastleigh by-election. Home Secretary Theresa May has a list of 130 criminal justice measures the Government wants to take back from Brussels. Ministers will then opt back in to some measures later. But talks have threatened to break down, with Tories wanting to quit almost all of the EU rules while Lib Dems want to remain sign up to many more. After meeting crime campaginers today, Mr Clegg warned national security could be at risk if Britain pulled out of 'essential' crime-fighting measures. The Deputy Prime Minister said: 'While some measures of European co-operation on crime are old, out of date or defunct, the police and other law enforcement agencies consistently tell us that other measures are essential for our national security and public safety. The European Arrest Warrant is one of those key measures. Without it, victims of crime like Maggie may never have seen those who beat her son nearly to death brought to justice, and as the police say, without it Britain could become a safe haven for Europe's criminals. We want to improve the way the arrest warrant works. That's why we're introducing some changes domestically, and why we're talking to our European partners about reform. But this key crime fighting tool should be reformed, not abandoned. Britain has a long and proud track record of leadership in the fight against organised crime and illegal immigration. I want to see us continuing to lead internationally on this agenda in to the future. The European arrest warrant allows the UK to extradite swiftly criminals from other EU member states. David Cameron needs Lib Dem votes to win a Commons vote on the issue. Mr Clegg today campaign groups Justice Across Borders and Anti-Slavery UK. They were joined by former Crimewatch presenter Nick Ross and Maggie Hughes, whose son Robbie was severely beaten in Crete in 2008. Mr Hughe's attackers were brought to justice in 2012 after being arrested in the UK under a European Arrest Warrant. After the meeting, Ms Hughes said: 'We need to keep what we've already got, because without the European arrest warrant we may never have got the suspects back to Greece and justice for Robbie. 'My son's ability and other people's children's ability to get justice should not be threatened by ideological battles in Westminster. No one has told me what the good reasons are to pull out of this cooperation, and Mr Clegg agreed we must protect the EAW and other important measures. David Cameron is under pressure from his MPs to quit more than 100 EU powers on crime and justice, but needs Lib Dem support to win a Commons vote In a speech last year Mr Clegg warned withdrawing from the arrest warrant would leave British police trying to fight crime 'to protect the British people with one hand tied behind their back'. 'Our police can call on the resources and intelligence of the entire European crime-fighting community to hunt down and arrest murderers and escaped convicts, to stop billions from being laundered out of the UK every year,' he said to Chatham House. 'To anyone who says we don't need these EU measures to fight crime and terrorism effectively, I say prove it. Prove it to the police, the intelligence agencies, the lawyers, the victims of crime charities. Prove it to the people who deal day in day out with the worst criminals imaginable. Because my position is clear: I will not ask them to protect the British people with one hand tied behind their back. Ahead of today's meeting, Justice Across Borders Director Thais Portilho-Shrimpton said: "We are a team of campaigners representing victims of egregious crimes perpetrated in the UK and abroad, including human trafficking and slavery. She added: "We hope to get assurances from the Deputy Prime Minister that the Lib Dems will not agree to this opt out and put in danger instruments such as the European Arrest Warrant and valuable agencies such as Europol, which has recently been asked by the UK to take the lead in investigating the horsemeat scandal." However, the Tories have made clear they will not sign up to a raft of Lib Dem demands leaving negotiaions on the verge of collapse. "The Lib Dems tend to err on the side of being more Europhile and we tend to want to sign up to as little as possible," said a Conservative source.