He said work would begin on finding ways to meet the conditions laid down by the Chilcot report on intercept evidence. But Mr Brown warned MPs this would involve "a substantial programme of work covering legal, operational and technical issues".

An unnamed "implementation team" within Whitehall will work alongside members of the Chilcot committee, led by former top civil servant Sir John Chilcot, to try to find a way of using evidence including phone-taps and the interception of other electronic communications, in prosecutions in England and Wales.

The report makes clear that agencies such as MI5 or the police should have a veto over whether material could be used in prosecutions.

Mr Brown told MPs in a Commons statement: "The use of intercept evidence characterises a central dilemma that we face as a free society - that of preserving our liberties and the rule of law, while at the same time keeping our nation safe and secure."

Previous prime ministers have turned down suggestions of using intercept evidence in court because of fears from the security services and the police that it risked tipping criminals off about their methods and would create a welter of paperwork.

But, publishing an edited version of the Chilcot Report, Mr Brown said: "It concludes that it should be possible to find a way to use some intercept material as evidence provided - and only provided - that certain key conditions can be met.

"These conditions relate to the most vital imperative of all, that of safeguarding our national security. The Government accepts this recommendation, and takes the accompanying conditions very seriously."

Tory leader David Cameron welcomed the report, but warned that the implementation body must not be a "talking shop for further delay".

Eric Metcalfe, of human rights and law reform group Justice, said: "We welcome the Prime Minister's announcement that the Government intends to lift the ban on intercept evidence. However, we wonder how much further work is really needed, given that the Government has privately been at work on ways of allowing intercept evidence for some time now."