The Home Office said the increase was partly due to a large number of arrests made following attacks in London and Manchester.
The number of suspects arrested in terrorism investigations has reached a record high, official figures reveal.
A total of 400 people were held for terror-related offences in Britain in the year to the end of September. This was the highest tally since data collection started in 2001 and a jump of 54% compared with the previous year.
The Home Office said the increase was partly due to a large number of arrests made following terrorist attacks in London and Manchester.
The 400 total includes 64 arrests made in connection with the Westminster (12), Manchester (23), London Bridge (21), Finsbury Park (one) and Parsons Green (seven) attacks.
A Home Office statistical bulletin said: “As a result, the number of arrests in the year to 30 September 2017 was the highest since the data collection began.”
The figures show that of the arrests made over the year: 115 (29%) resulted in a charge, of which 97 (84%) were charged with terrorism-related offences; 213 (53%) were released without charge; 60 (15%) were released on bail pending further investigation; 11 (3%) faced “alternative action”; and one case was pending.
It was also revealed that 58 of those held were female – the highest number on record.
There were year-on-year increases in the number of arrests for terrorism-related offences across all age groups and ethnic groups, including a 77% rise in the number of white suspects held, from 81 to 143.
The new figures show an annual jump of more than a third in arrests linked to international terrorism, from 212 to 292.
This category refers to activity linked to or motivated by any terrorist group that is based outside the UK which operates in and from third countries, such as Islamic State.
There was also a leap in arrests for “domestic” terrorism, up from 20 in the year to September 2016 to 73 in the latest period.
Domestic terrorism refers to activity where there are no links to either Northern Ireland-related or international terrorism. The remaining arrests were Northern Ireland-related (five) and unclassified (30).
Security Minister Ben Wallace said police and security services “have been clear that we are facing a shift rather than a short-term spike in the terrorist threat”.
He added: “The statistics we are publishing today demonstrate the breadth of work that they undertake, alongside the rest of the criminal justice system, day in and day out to keep us safe. But this is not the totality of our work. The whole of society must come together to challenge the terrorist threat.
“The public must remain alert but not alarmed and report any suspicions they have about unusual activity or behaviour to the appropriate authorities.
“Furthermore, the Government is reviewing its counter-terrorism strategy in light of recent attacks to ensure we meet the threat from terrorism now and in the future.”
Counter-terror agencies believe the scale of the threat facing the country is unprecedented.
Britain was hit by five attacks between March and September, while authorities are mounting more operations to disrupt suspected terrorist planning.
Home Secretary Amber Rudd disclosed earlier this week that MI5 and police have now thwarted 22 Islamist plots since the murder of Lee Rigby in May 2013.
This includes nine which have been foiled since the Westminster atrocity in March.
The number of “live” operations being run by MI5 and police has surged by a third since the beginning of this year to well over 500.
These probes involve around 3,000 “subjects of interest”, while there is a further pool of more than 20,000 individuals who have previously been investigated.
Earlier this week an official assessment revealed the ringleader of the London Bridge rampage was being “actively” investigated at the time of the atrocity.
It also found that the Manchester bombing in May could have been stopped “had the cards fallen differently”.
Once your comment has been submitted, it won’t appear immediately. There is no need to submit it more than once. Comments are published at the discretion of Bailiwick Publishing, and will include your username.
There are no comments for this article.