The Conservative party is preparing to make a decision as they consider leaving the EU’s fast-track extradition scheme, which helped bring failed London bomber Hussain Osman to justice, as a part of their quest to avoid giving up any further  sovereignty to the EEC.

Any such decision would certainly find favour with the Eurosceptics, following Cameron’s decision not to hold a referendum on the Lisbon treaty last week, but it will alarm police chiefs and law enforcement agencies, who believe the European arrest warrant is a key part in fighting domestic and cross-border crime.

The warrant, which operates between EU member states and speeds up extradition cases, has been credited with helping to dismantle the “Costa del Crime” – British criminals fleeing to Spain for safety from prosecution – and of bringing some of Europe’s most dangerous criminals to justice.

At the moment the warrant is operated “inter-governmentally” by ministers from each of the 27 EU member states, but does not come under the European Commission, European Parliament, or European Court of Justice, but when the Lisbon Treaty comes into force, justice and home affairs matters will be brought under full EU control over a five-year period.

Experts say that, because amendments will soon be needed to the way the warrant operates, it will probably be switched to full EU control long before 2014. When this happens, the British government will have to decide whether or not to “opt in”.

Last night, Alan Johnson, the home secretary, said the Conservatives decision not to commit to the warrant scheme is a misjudgement:

“In 2005, it was only because we had the European arrest warrant that we could fast-track the extradition of Hussain Osman to Britain. Do the Tories seriously think it would have been better for Britain to have made it harder for the police to get their man? Their European obsession would put Britain at risk.”

Liberal Democrat Shadow Foreign Secretary, Edward Davey accused the Tories of putting their ideological opposition to the EU above the pursuit of criminals and terrorists.

“Anyone who has looked at the facts knows that, before the arrest warrant, co-operation with many EU countries on catching these serious criminals was at best patchy, at worst impossible. British police simply couldn’t rely on Interpol or any bilateral arrangements to deliver justice, even when the offences were as serious as murder, rape or child abuse, Edward Davey said.

“When it’s about co-operating to bring drug smugglers, murderers and paedophiles to justice, it’s unforgiveable that Cameron would be prepared to put his Euroscepticism above the safety of our young people and the security of the streets. If the Tories were to take the UK out of the agreement, Cameron would be giving the green light to the restoration of Spain’s ‘Costa del Crime’ and all the other European hideouts for Britain’s most serious criminals,” Edward Davey