Kim Sengupta: Others in the Jihadist chain warranted sharper focus from MI5

"We can only hit the crocodiles nearest to the boat," was the untypically florid description by Jonathan Evans, the head of MI5, of the problems faced by his service in the "war on terror". Despite receiving sizeable reinforcements, the sheer scale of the threat means that it is currently impossible, he maintained, to track each and every suspect.

The situation in the period preceding 7/7 was even more difficult. Five years ago, when Siddique Khan and Shehzad Tanweer first crossed MI5's radar, the service could only devote full resources to investigating 6 per cent of the targets. Some 60 per cent of their targets were allocated "inadequate" resources, or "none" – a state of affairs the Intelligence and Security Committee found "astonishing".

Khan and Tanweer went on to carry out the London bombings, killing 52 people and injuring 1,000 others – Britain's introduction to suicide bombing and the grim realisation that the enemy was not just in the mountains of Pakistan and Afghanistan, but here in our midst.

Yesterday's report refused to blame MI5 for failing to stop the attacks. The MPs accepted the service's explanation that they simply did not have the resources to monitor Khan and Tanweer, who were judged to be merely in the fringes of groups planning attacks.

Others disagree. Members of bereaved families were expressing their disquiet and disappointment at what they saw as lack of answers. David Davis, the former shadow Home Secretary, and his successor Chris Grayling, called for a senior judge to carry out an inquiry.

Are they right? What we do know is that MI5 had come across Khan at least nine times and that he was associated with Omar Khyam, who was arrested in 2004 for plotting to blow up nightclubs and shopping centres; that there were 10 separate sets of communications about Khan between MI5 and West Yorkshire police; that Khan was photographed, but not identified, eight years ago at an outdoor training course run by a Muslim fundamentalist; that Khan and Tanweer were overheard discussing raising money through fraud and travelling to Pakistan; and that Tanweer, in turn, was recorded in Khyam's car praising the Madrid bombings, but it took four years to fully transcribe the tape.

This may seem like damning evidence which should have at least led to the apprehension of Khan. But the sobering facts are that there were many others in the jihadist chain who warranted much sharper focus from MI5's scarce resources – there were prospects of more imminent murders.

What the ISC report does not address, however, was how this state of civil war actually came about. For years violent Islamist groups were based in this country, some of them carrying out attacks abroad. This was tolerated in the belief that they would not attack their own home and that, as long as they were here, the security services would be able to infiltrate them. At the same time, mosque after mosque was taken over by radicals with the authorities refusing pleas for help from moderate Muslims saying they did not want to interfere in community matters. There was even a name for this accommodation: the "covenant of security".We now know, of course, that jihadists will indeed blow up their own home countries and that the security agencies signally failed to infiltrate the terrorist cells.

Since the London bombings there have been around a dozen serious terrorist attempts to commit mass killing. Most of them have been foiled. But security officials acknowledge that this is unlikely to remain the case. MI5 currently employs 3,500 staff. The ISC pointed out it would actually need "several hundred thousand" to provide comprehensive intelligence coverage on terrorists. That is the grim reality on the ground in the age of global jihad and the price one pays for the cynical policy of the past.