British intelligence officials say there could be 200 potential suicide bombers in the country, many waiting to strike during the 2012 Olympic Games in London.
Senior intelligence officials called the figure a "conservative estimate" and that the network behind them could involve up to 2,000 active Britain-based Islamist extremists.
Train stations or public events are the most likely targets, the Telegraph reported, rather than Olympic venues where high security measures will make it more threaten the success of their operations.
Earlier this year, classified documents disclosed by Wikileaks predicted an increase of suicide bombers by British-based Islamists who had recently received training in terrorist camps located in Pakistan, the Telegraph reported.
The information is believed to stem from a report on the enduring terrorist threat despite the death of al-Qaida leaders including Osama bin Laden. Officials are actively investigating suicide bomb plots, as seen in recent charges against six men from Birmingham.
Some plotters may be stopped by either a 'chance encounter' or by an intelligence-led investigation," an unnamed intelligence officer said. He added "that if a terrorist cell was properly organized and secure there was very little the authorities could do to prevent an attack."
Meanwhile, recent budget cuts may enable terrorists to more easily evade detection and actively plot attacks. In addition, "up to 70 jailed terrorists being freed this year may not be monitored properly due to cuts in services," the UK-based Sun reported.
"These men required maximum supervision and we won't be able to do it," said Harry Fletcher, of the National Association of Probation Officers.
The potential bombers live freely, the Telegraph reported, actively planning attacks.
The report comes as Syria's grand mufti threatened a wave of suicide bombings in Europe and the United States should Western governments attack Bashar al-Assad's dictatorship. Syrian Grand Mufti Ahmad Badreddine Hassoun, a staunch Assad supporter, made the threats Sunday night in a speech translated by the Middle East Media Research Institute (MEMRI).
"I say to all of Europe, and to the U.S.: We will prepare martyrdom-seekers who are already among you, if you bomb Syria or Lebanon," Hassoun said.