The intelligence services and the police will have a veto on evidence from phone taps being used in courts, under plans to allow intercept material in criminal proceedings.

Gordon Brown paved the way for material from intercepts to be used in courts but set up a series of hurdles, including giving a veto to MI5, MI6, GCHQ and the police.

He said work would begin on finding ways to meet the stringent conditions laid down in an edited report on intercept evidence by a team headed by Sir John Chilcot, former permanent secretary at the Northern Ireland Office, published yesterday.

Mr Brown told MPs that though the report concluded that it should be possible to find a way to use “some intercept evidence” in prosecutions in England and Wales, important conditions to safeguard national security had to be met. He told MPs in a statement that this would involve “a substantial programme of work covering legal, operational and technical issues”. An “implementation team” within Whitehall will work alongside members of the Chilcot committee to try to find a way round these problems.

David Cameron, the Tory leader, said the implementation body must not be a “talking shop for further delay”. He said: “At the end of the day, this is a political decision and that has got to be made by a politician. That means him [Mr Brown]. It is clear what needs to be done: intercept in court so we catch, convict and imprison more terrorists. We must not put off endlessly what needs to be done.”

The report from Sir John recommends nine conditions to be met before any change is made, which could limit the practical effect of lifting the current ban on intercept material being used as evidence in courts.

The crucial condition states: “The intercepting agency shall decide whether a prosecution involving their intercepted material shall proceed.”

Among other conditions is that no intelligence or law enforcement agency should be required to transcribe or make notes of intercepted material to a substantially higher standard than it believes to meet its objectives. This means that they would not have to produce material to the standard required for it to be used as evidence.

Another condition is that in trials, defence lawyers should be banned from “fishing expeditions” against intercept evidence held by any agency.

The report discloses that officers operating the present system have “substantial fears” that a change in the law could damage national security.

The Association of Chief Police Officers is opposed to allowing intercept evidence because of its potential effect on counter-terrorism and cases such as kidnappings. The Metropolitan Police and police in Scotland and Northern Ireland have a similar view.

Officers in the Metropolitan Police conducted a review of cases in 2006-07 which involved interception and concluded that a change in the law would have increased the conviction rate from 88 per cent to 92 per cent, the report said.

It said that the Crown Prosecution Service believed there would be more guilty pleas under a regime that allowed defendants’ own words to be played to a jury, because criminals would “realise that their case is hopeless”. More criminals might also turn “supergrass” as a result, it said.

Campaigners have said using phone-tap evidence would reduce the need to impose control orders on suspects by enabling them to be tried instead. But a review of nine control order cases found that in four cases the intercepted material would not have been of evidential value, and in the other five, using the evidence in open court would have damaged national security.

The report disclosed that the Home Office is leading a new programme to update Britain’s ability to intercept phone calls and electronic communications, triggered by the proliferation of internet-based communications.

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