Jonathan Evans says draft bill is necessary to ensure police and intelligence services keep technological pace with criminals
It would be "extraordinary and self-defeating" if intelligence agencies and police were not allowed to keep pace with terrorists and criminals, the head of MI5 has said in response to the row over the draft communications bill.
In his first speech for two years, Jonathan Evans gave a stout defence of the bill, which critics have described as a "snoopers' charter" because it extends the breadth of the material that internet service providers must keep.
Under the proposals, records will be kept of all internet use, including activity on social networking sites, as well as details of mobile phone calls and texts. This information will have to be kept for a year at a minimum cost to the government of £1.8bn.
In the inaugural defence and security lecture in London on Monday night, Evans made a rare public foray into a toxic political subject, insisting that the proposals were "necessary and proportionate … to ensure that crimes, including terrorist crimes, can be prevented, detected and punished".
"It would be extraordinary and self-defeating if terrorists and criminals were able to adopt new technologies in order to facilitate their activities while the law enforcement and security agencies were not permitted to keep pace with those same technological changes."
Evans defended measures in the equally controversial justice and security bill, which would prevent intelligence being disclosed in open court.
Currently going through parliament, the bill envisages secret hearings in civil cases, known as closed material procedures (CMPs). Though this would protect certain sensitive material being made public, it has caused deep unease among senior lawyers and constitutional experts because it means defendants or claimants will not be allowed to see all the evidence gathered against them.
MI5's director general said secrecy remained "essential if we are to avoid our opponents knowing whether they are on our radar and learning how we go about our work".
"At present our ability to account for our actions in the courts is constrained by the fact that sensitive national security-related material … can only be considered in open court. This means that such material cannot in practice go into court at all.
"This situation is bad for us, bad for the other party to proceedings, and bad for the administration of justice."
The new measures would mean "more rather than less material will go before the courts", he said. "But the sensitive material will be protected. This will mean better justice and better accountability."
Evans's intervention reflects frustration around Whitehall about the recent furore over data retention. It is understood there has been concern within MI5 and the police that the government was caught flat-footed by leaks about the legislation, and was too slow to set out the case in favour of changes.
Evans said he needed to challenge "the perception in some areas that the terrorist threat has evaporated" because there hadn't been a major attack in the UK for seven years.
He admitted that a form of stalemate was developing in counter-terrorism. "They haven't stopped trying but we have got better at stopping them."
But, he said, "in backrooms and in cars and on the streets of this country, there is no shortage of individuals talking about wanting to mount terrorist attacks here. Our assessment is that Britain has experienced a credible terrorist plot about once a year since 9/11. So the threat is real and remains with us today."
Evans's remarks come amid political debate over the implications for civil liberties and privacy posed by the two bills.
Under the draft communications and data bill, police and the intelligence agencies will be able to access "header" information, including email addresses and mobile phone numbers. They will not be allowed to access the content of emails, texts and mobile phone calls without a warrant signed by the home secretary. However, it is still unclear whether it is technically feasible to separate material in this way.
Senior Tories and Liberal Democrats have joined human rights groups raising concerns about the need to store so much data. They point out that the police and intelligence services already make up to 500,000 requests for data every year, and this is likely to rise.
David Davis, the Conservatives' former shadow home secretary, has argued that serious criminals would quickly find other ways to communicate and the only people it would catch were the innocent and the incompetent.
He described the proposals as "incredibly intrusive", adding: If they really want to do things like this, and we all accept they use data to catch criminals, get a warrant. Get a judge to sign a warrant, not the guy at the next desk; not somebody else in the same organisation."
Liberty said the "argument for the snoopers' charter is that we must all compromise our privacy because crime sometimes happens on the web".