Only one in four terror suspects were charged with a terrorism-related offence last year, figures showed.
A total of 130 people were arrested on suspicion of being involved in terrorism in the 12 months to September 2010, but only 36 were charged with a terror-related offence.
Almost one in two were released without charge, the figures published by the Home Office showed.
The number of terror-related arrests also fell 35% compared with 201 in the previous 12 months.
None of the suspects were held in pre-charge detention for more than 14 days and more than three in five were dealt with within 48 hours, the figures showed.
A total of 1,897 terrorism arrests have been made since the 11 September terror attacks in the United States in 2001, with 420 charged with terrorism-related offences and 240 convicted. Of the others, 32 were still awaiting prosecution at the end of December.
The figures also showed that 20 prisoners convicted of terro