An armed police officer in London
The Home Office has revealed a record 299 suspected terrorists were arrested in the 12 months to MarchGetty Images

The Home Office has revealed a record 299 suspected terrorists were arrested in 2014, the most since 9/11. More women were arrested than ever before under the Terrorism Act, while the number of 18 to 20-year-olds suspected of terror offences more than doubled.

The figures related to arrests made in the UK in the year to March and reveal a 31% increase overall on the previous year. It is the highest number since data collection began in September 2001. There were 35 women arrested over the period, largely accounted for by a spike in the six months to March 2015.

In comparison, between 11 September 2001 and the year ending 31 March 2013, 7% of those arrested were female. In the most recent two years, 12% of those arrested have been female. Britons made up almost 78% of those arrested for terrorism-related offences, up 4% on the previous year. Those of Asian ethnic appearance accounted for 140 (47%) arrests, up 36% on the previous 12 months.

Of the 299 arrested in 2014, 118 were charged with an offence, 100 of which (85%) considered to be terrorism-related. The report said this high percentage suggested police were "more frequently able to find evidence to support the link to terrorism following a terrorism-related arrest".

Last year saw only 43% of all those arrested being released without charge, below the overall figure of 52% since records started in 2001. Terror arrests spiked in the wake of the attacks on the World Trade Center and the Pentagon in 2001 as well as after the July 7 bombings in London and the Arab Spring of 2010.

Terror arrests 2014-15

118 charged

130 released without charge

11 alternative action (includes transfers and proceedings under mental health legislation)

40 bailed

"Since 11 September 2001, the numbers of terrorism-related arrests have fluctuated," the report said. "There was an initial spike in the number of arrests in the period soon after the September 11 attacks on the US, and around the time that the US-led invasion of Afghanistan was beginning.

"There was a large increase in the number of arrests in the period immediately after the 7 July London bombings, where the number of arrests was at its highest since the data collection was established. Soon after this, the number of terrorism-related arrests declined, until late 2010. In late 2010, the Arab Springs began, and throughout the years since the initial uprising, the number of terrorism-related arrests in Great Britain has seen a steady rise."