A new attempt to allow phone tap evidence to be used in court cases has been made in the House of Lords.
Phone tap evidence is presently not admissible in court
Britain is one of the few Western nations not to admit such evidence in criminal trials.
Metropolitan Police chief Sir Ian Blair backs its use but intelligence chiefs are against it, arguing it could cost too much and jeopardise operations.
Opening the debate, Lord Lloyd said it would eventually save money as it would cut the length of trials.
The former law lord, a crossbench peer who reviewed terrorist law for the Conservative government in 1995, is introducing his Interception of Communications (Admissibility of Evidence) Bill.
He said: "The question comes down simply to this: can we or can we not do it safely? Can we find a way of making evidence admissible without prejudicing what we have already got? And my answer is yes we can."
He dismissed the argument that it would stop criminals using the phone to communicate - as that had not happened in other countries where phone tap evidence was used in court.
He agreed there would be "resource implications" - the intelligence services argue that someone with high security clearance would have to sift through all the evidence.
But he said it could lead to shorter trials and more guilty pleas, adding: "If we are to be serious about convicting criminals ... we must not let resource implications stand in the way."
Among those opposing the bill was another crossbencher, Lord Boyd of Duncansby - although he said he would back it if the concerns of the security services were met.
He told the House that phone tapping would only lead to a small increase in convictions - but would have a large effect on resources.
Peers were told that the recent trial of crime boss Terry Adams, a transcription of eavesdropping material, at the request of the defence, had reportedly cost £1.9m.
And Labour's Baroness Ramsay, a former MI6 officer, argued: "The slightest hint of interception risks revealing the techniques involved on that particular target and similar targets will immediately be assumed vulnerable."
"The loss of access is instant and it's usually permanent."
But Lib Dem peer Lord Thomas of Gresford said his party backed the bill and said a system of Public Interest Immunity Certificates would stop criminals from learning about the techniques that had been used against them.
For the Conservatives, Lord Henley also offered the bill his full support and said it was time the government justified the "poverty" of its approach on the issue.
The Bill got an unopposed second reading, but without government support will not become law.
Home Office Minister Baroness Scotland said the government would change the law, if the correct safeguards could be put in place.
But she said the Bill as it stood represented "potentially very dangerous and very real threats to our ability to maintain our fight against serious crime and terrorism".