Up to 4,000 terrorism suspects and their supporters are active in Britain, the former Metropolitan Police Commissioner Lord Stevens has said
Lord Stevens said the security service MI5 had recently suggested a figure of 2,000 but the true number was "probably nearer 4,000".
Police and MI5 were "still too underfunded and undermanned to cope with the task they face in the decades to come. And that's how long this will last," he said.
The "infection" had spread out from "hot spots" such as Luton, the West Midlands and Finsbury Park in London and those involved in the fertiliser bomb plot case which finished this week were "ordinary and British".
Lord Stevens also gave warning that al-Qa'eda-linked extremists were already trying to infiltrate the police and the security services and that dozens had already been weeded out.
He urged that known terrorism suspects and "hate clerics", such as Abu Hamza and Abu Qatada, should be deported, adding: "Our human rights come first. Yet, incredibly, our so-called Human Rights laws, and our enviable history of religious tolerance, mean that foreigners preaching death and destruction to our way of life are allowed to stay here because their own countries won't tolerate such evil."
In his column in The News of the World, after five terrorists were jailed for life in the fertiliser bomb case - which began as Operation Crevice for Scotland Yard when he was still Commissioner - Lord Stevens called for an independent Parliamentary committee "to publicly oversee the security services".
This task is currently carried out by the Intelligence and Security Committee (ISC), which reports to the Prime Minister.
Police and security services, he added, had "nothing to hide. But it's vital the public know that". There is controversy over how MI5 handled intelligence over links between the fertiliser gang and Mohammed Sidique Khan, the ringleader of the July 7 bombers.
It was claimed yesterday that al-Qa'eda extremists, including Khan, held a "summit" in London four years ago, at a barbecue, and plotted activity in Britain. The claims in The Sunday Times are attributed to Hassan Butt, a one-time radical now said to have turned his back on fundamentalist violence,
Butt - a former spokesman for the now defunct al-Muhajiroun extremist group founded by Omar Bakri Mohammed - claimed the barbecue took place in late April 2003, after the invasion of Iraq and that he also met Mohammed Junaid Babar, an American jihadist who was the principal "supergrass" witness for the Crown in the fertiliser case at the Old Bailey.
It emerged in the trial that Khan, Babar and members of the fertiliser gang had attended a training camp in the Afghan border region in July 2003.
It has also emerged that anti-terrorism police made inquiries around five months before the July 2005 bombings into two cars which were shown to be linked to Khan.
The checks were carried out by Scotland Yard detectives as part of the preparation of the fertiliser case.
Khan's own Honda and a courtesy car loaned to him by a garage cropped up during a surveillance operation in February and March 2004.
4,000 suspected jihadists in UK