"The security service believes that since the attacks on July 7, 2005, around 40 terrorist plots have been disrupted. There have been attempts to conduct marauding Mumbai-style gun attacks on our streets, blow up the London Stock Exchange, bring down airliners, assassinate a British ambassador and murder serving members of our armed forces," UK home secretary Theresa May said.
The deadly series of shootings and bombings in Mumbai in November 2008 killed at least 166 people.
She also revealed that counter-terrorism officers have made 753 arrests since May 2010 - resulting in 138 terrorists being jailed and 13 people being extradited.
Speaking at a counter-terrorism event in London, she told an audience "the time is right" for enhanced security measures.
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Unveiling a new counter-terrorism bill that will now be fast-tracked through the British Parliament, she said schools, universities and councils will be required to take steps to counter radicalisation.
Scotland Yard Assistant Commissioner Mark Rowley said, "Police officers and our partners are continuing to work 24 hours a day, seven days a week to protect the UK from a terrorist attack.
"So far this year, we have disrupted several attack plots and made 271 arrests following counter-terrorism investigations, but the eyes and ears of law enforcement and other agencies alone cannot combat the threat," he said.