LONDON: British would-be jihadists are heading to the Middle East to seek terrorist training because parts of the Arab world have “once more become a permissive environment for Al Qaeda”, the head of MI5 has warned.

Jonathan Evans said this was a “new and worrying development and could get worse as events unfold ... some will return to the UK and pose a threat here”.

Though Evans did not say how many people from the UK had gone to the region, it is believed the agency has monitored more than 100 who have attempted to link up with extremists in countries such as Yemen, Egypt, Syria and Libya.

A few Britons have also travelled to the horn of Africa, in particular Somalia.

In a speech in London on Monday night, Evans said one byproduct of the Arab spring was giving Al Qaeda a chance to re-emerge in the countries where the network first won popular support.

In the long-term, more democracy should “ease some of the pressures that have spawned extremism in the region”, he said, but in the short-term, with the Arab world in radical transition, this “more immediate problem has emerged”.

“This is the completion of a cycle,” said Evans. “Al Qaeda first moved to Afghanistan in the 1990s due to pressure in their Arab countries of origin. They moved on to Pakistan after the fall of the Taliban. And now some are heading home to the Arab world again. And a small number of British would-be jihadis are also making their way to Arab countries to seek training and opportunities for militant activity.”

The scale of terrorist ambition emerging from Yemen is believed to be at the top of MI5's worry list, and the director general made particular reference to recent plots believed to have been hatched in the country. “Repeated attempts by Al Qaeda in Yemen to mount attacks on aircraft, as we have seen in the underpants bombs and the bomb found in a printer cartridge at East Midlands airport, could have caused mass civilian casualties.”

Evans said he needed to challenge “the perception in some areas that the terrorist threat has evaporated” because there hasn't been a major attack in this country for seven years.  He admitted they were now “reaching a form of stalemate” in counter-terrorism. “They haven't stopped trying, but we have got better at stopping them.”

But he said “in back rooms 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.

Evans defended proposals in the draft communications bill, which critics have described as a “snoopers charter” because it extends the breadth of the material internet service providers must keep - and makes it available for investigators. As well as details of mobile phone calls and texts, the proposals cover internet use, and activity on social network sites.

Evans insisted the proposals were “necessary and proportionate” to ensure crimes could be prevented 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 said the measures in the justice and security bill were also vital. This envisages secret hearings in civil cases. Although this would prevent certain sensitive material being made public, it means defendants or claimants will not be allowed to see all the evidence against them. Evans 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”.

Evans's comments reflect frustration within the intelligence community over the debate on data retention. It is believed there has been concern 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.  His remarks come amid anguished political debate over the implications for civil liberties and privacy.

Under the communications and data bill, 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 without a warrant signed by the home secretary.

By arrangement with the Guardian