1600 young British Muslims under MI5 surveillance for plotting terror

Eliza Manningham Buller delivered a stark assessment of the threat facing the country from 200 terror networks stretching from the UK to Pakistan, including 30 "Priority 1" plots.

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In August Home Secretary John Reid claimed to know of 24 "major conspiracies", suggesting the dangers posed by organised terrorists is growing.

Delivering the Government's latest assessment of the terror threat, the Director General of the Security Service revealed that her agency's caseload has increased by 80 per cent since January.

She said: "That threat is serious is growing and will, I believe, be with us for a generation. It is a sustained campaign, not a series of isolated incidents. It aims to wear down our will to resist."

Her assessment comes just days before Tony Blair unveils the legislative programme for his final Parliamentary session as Labour leader and Prime Minister.

Wednesday's Queen's Speech is widely expected to be dominated by a raft of new security measures. Many will see Dame Eliza's speech as part of a co-ordinated Government publicity offensive to build up the case for new anti-terror legislation.

In remarks to academics this week that were released last night, she described how young Muslims are being radicalised and turned into potential suicide bombers.

"More and more people are moving from passive sympathy towards active terrorism through being radicalised or indoctrinated by friends, families, in organised training events here and overseas," she said.

"Young teenagers are being groomed to be suicide bombers." She said she was alarmed by the "scale and speed" of the radicalisation, which is said to have intensified since last year's July suicide bombings in London.

She said: "It is the youth who are being actively targeted, groomed, radicalised and set on a path that frighteningly quickly could end in their involvement in mass murder of their fellow citizens, or their early death in a suicide attack or on a foreign battlefield.

"Killing oneself and others in response is an attractive option for some citizens of this country and others around the world."

Dame Eliza revealed that despite an intense recruitment drive, just six per cent of MI5's staff are from ethnic minorities, compared to eight per cent for the Metropolitan Police. However, of the 400 new recruits this year, 14 per cent are non-white.

Her address followed this week's conviction of Dhiren Barot, the al-Qa'eda terrorist sentenced to 40 years for planning ambitious bomb attacks on London.

Dame Eliza predicted that terrorists would become more sophisticated in their methods. "Today we see the use of home-made improvised explosive devices. Tomorrow's threat may, and I suggest will, include the use of chemical, bacteriological agents, radioactive materials and even nuclear technology."

She added: "My officers and the police are working to contend with some 200 groupings or networks, totalling over 1600 identified individuals (and there will be many we don't know) who are actively engaged in plotting or facilitating terrorist acts here and overseas."

Some of the networks were directly linked to al-Qa'eda in Pakistan, which used the Pakistani community in Britain to recruit and promote terrorists.

Since the 7 July bombings, five further major conspiracies in the UK had been thwarted, the director general added.

Out of the 200 or so groups being watched by MI5, a smaller subset are of the highest priority because its feared that they are plotting actual attacks.

"We are aware of numerous plots to kill people and to damage our economy. What do I mean by numerous? Five? Ten? "No, nearer 30 that we currently know of," she said.

MI5 has increased in size by nearly 50% since 9/11 and now stands at roughly 2,800 staff. "I wish life were like Spooks (the TV series) where everything is, a, knowable, and, b, soluble by six people," she explained.

"We cannot focus on everything so we have to decide on a daily basis with the police and others where to focus our energies, whom to follow, whose telephone lines need listening to, which seized media needs to go to the top of the analytic pile.

"Because of the sheer scale of what we face - my service has seen an 80% increase in casework since January - the task is daunting.

"We shan't always make the right choices. And we recognise we shall have scarce sympathy if we are unable to prevent one of our targets committing an atrocity."

Dame Eliza was speaking yesterday morning to a small audience from the Mile End Group, an academic seminar group at the History department of Queen Mary, University of London.