Official figures show there were 304 arrests for terrorism-related offences in Great Britain in the year to the end of March this year.
This was an increase of 18% on the previous 12 months, and the highest number in any financial year on record since data collection started in September 2001.
Of the 304 arrests, 108 resulted in a charge, including 91 suspects charged with terror-related offences.
One hundred people were released without charge, 88 were bailed pending further investigation and eight faced “alternative action”.
The tally for 2016/17 includes 12 arrests made as part of the investigation into the Westminster attack in March. All were released without charge and told they would face no further action.
Since the Westminster atrocity there have been two more deadly attacks, in Manchester and London Bridge, while counter-terror agencies have foiled five alleged plots.
The scale of the threat facing the country has been laid bare with figures showing police and MI5 are involved in 500 investigations involving 3,000 individuals at any one time.
There are also 20,000 former “subjects of interest” whose risk must be kept under review.