Newly-released Home Office figures show there were a record 412 arrests for suspected terrorism-related offences in Britain in 2017.
The number of arrests made last year represents an increase of 58% compared with 261 the previous year, the figures show.
It is the first time the tally for a calendar year has been above 300.
A Home Office bulletin said the increase was partly due to a large number of arrests after attacks in London and Manchester.
Security minister Ben Wallace said: ‘Today’s figures are, once again, testament to the breadth of work undertaken by the police, Security Service and wider judicial system in identifying and stopping terrorism in our communities and bringing those responsible to justice.
‘The police and Security Service have been clear about the scale of the threat we face.’
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He added: ‘We will continue to work with them and other agencies to ensure we have a broad response to all forms of terrorism both now and in the future.
‘The public should remain alert but not alarmed and report any suspicions they have about unusual activity or behaviour to the appropriate authorities.’
There were several high-profile terror attacks in the UK in 2017.
In March, Khalid Masood drove a car into pedestrians on Westminster Bridge, before he crashed the vehicle into the Palace of Westminster’s perimeter and stabbed a policeman to death.
The Manchester Arena terror attack in May saw suicide bomber Salman Abedi blow himself up at an Ariana Grande concert, resulting in the deaths of 22 individuals.
Less than two weeks later, three terrorists drove a white van at high speed across London Bridge, running into groups of people, before crashing.
The occupants then ran to nearby Borough Market, where they stabbed more people before they were killed by armed police.