Metropolitan Police Commissioner Sir Ian Blair has called for a shake-up in the way courts deal with terror trials.
Sir Ian Blair wants a review of the 28-day limit on holding terror suspects
He told a summit in Germany that changes to the law were needed to speed up cases and to prevent convictions being held back from the public.
Sir Ian also said the 28-day limit for holding terror suspects needed to be reviewed in the near future.
His comments follow the security service's warning that the terror threat was "serious" and "growing".
On Friday, MI5 chief Dame Eliza Manningham-Buller said the security service knew of 30 terror plots threatening the UK and was keeping 1,600 individuals under surveillance.
Speaking at the Urban Age summit in Berlin, Sir Ian said the criminal justice system was "creaking under the impact" of terror trials.
One alleged major conspiracy was due to take two years and eight months to reach court, he said.
He added that British contempt of court laws needed to be changed. Under current laws, there is a ban on publishing details from one case that may prejudice another - which Sir Ian said stopped the public seeing justice being done.
He also reiterated calls for phone tap evidence to be used in court, for consideration of ban on people covering their faces and burning flags at demonstrations and for a rule change to allow suspects to be quizzed after charge and intercept evidence allowed in court.