The United Kingdom will adopt a measure aiming to strengthen cooperation among European police forces, Home Secretary Theresa May announced on 27 July 2010.
The European Investigation Order (EIO) will simplify the process for seeking assistance from other nations' forces and provide formal deadlines for the execution of requests.
In a statement to the Commons, Mrs May said the EIO would replace the current mutual legal assistance (MLA) agreements, which she said were flawed and "confusing for the police and prosecutors".
In one drug trafficking case, she said, "the evidence arrived in the UK after the trial had been completed".
The home secretary acknowledged the existing draft EIO was "not perfect" but by opting-in at this stage "we have the opportunity to influence its precise outcome", she said.
The final version of the order should include "a proportionality test, so that police forces are not obliged to do work in relation to trivial offences", she argued.
"I want to be clear that the EIO will not allow foreign authorities to instruct UK police officers on what operations to conduct, and it will not allow foreign officers to operate in the UK with law enforcement powers," Mrs May added.
But Conservative backbencher Jacob Rees-Mogg asked her "how can we be certain that we won't cede powers to Europe?"
He recalled the words of Tory former prime minister Lady Thatcher who, when "Europe was trying to snatch powers once said 'no, no, no"'.
Mr Rees-Mogg asked: "Isn't that a much preferable way of approaching further European powers?"
Mrs May said other European states shared the concerns that the UK had over parts of the draft directive, making ministers confident they could agree a text meeting all their requirements.
In her statement, Mrs May told MPs: "The EIO will allow us to fight crime and deliver justice more effectively.
"It does not amount to a loss of sovereignty. It will not unduly burden the police. It does not incur a loss of civil liberties.
"It is in the national interest to sign up to it."
The statement was welcomed by shadow home secretary Alan Johnson.
He claimed that the Conservatives "had opposed the European arrest warrant principally, I believe, because it contained the word 'European'.
"I'm glad you aren't repeating that mistake," he told Mrs May.